--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -33,7 +33,7 @@ obj-$(CONFIG_ARCH_REALVIEW)		+= irq-gic-
 obj-$(CONFIG_ARM_GIC_MSI_LIB)		+= irq-gic-msi-lib.o
 obj-$(CONFIG_ARM_GIC_V2M)		+= irq-gic-v2m.o
 obj-$(CONFIG_ARM_GIC_V3)		+= irq-gic-v3.o irq-gic-v3-mbi.o irq-gic-common.o
-obj-$(CONFIG_ARM_GIC_V3_ITS)		+= irq-gic-v3-its.o irq-gic-v3-its-platform-msi.o irq-gic-v4.o irq-gic-v3-its-msi-parent.o
+obj-$(CONFIG_ARM_GIC_V3_ITS)		+= irq-gic-v3-its.o irq-gic-v4.o irq-gic-v3-its-msi-parent.o
 obj-$(CONFIG_ARM_GIC_V3_ITS_FSL_MC)	+= irq-gic-v3-its-fsl-mc-msi.o
 obj-$(CONFIG_PARTITION_PERCPU)		+= irq-partition-percpu.o
 obj-$(CONFIG_HISILICON_IRQ_MBIGEN)	+= irq-mbigen.o
--- a/drivers/irqchip/irq-gic-v3-its-msi-parent.c
+++ b/drivers/irqchip/irq-gic-v3-its-msi-parent.c
@@ -4,6 +4,7 @@
 // Copyright (C) 2022 Linutronix GmbH
 // Copyright (C) 2022 Intel
 
+#include <linux/acpi_iort.h>
 #include <linux/pci.h>
 
 #include "irq-gic-common.h"
@@ -93,6 +94,68 @@ static int its_pci_msi_prepare(struct ir
 #define its_pci_msi_prepare	NULL
 #endif /* !CONFIG_PCI_MSI */
 
+static int of_pmsi_get_dev_id(struct irq_domain *domain, struct device *dev,
+				  u32 *dev_id)
+{
+	int ret, index = 0;
+
+	/* Suck the DeviceID out of the msi-parent property */
+	do {
+		struct of_phandle_args args;
+
+		ret = of_parse_phandle_with_args(dev->of_node,
+						 "msi-parent", "#msi-cells",
+						 index, &args);
+		if (args.np == irq_domain_get_of_node(domain)) {
+			if (WARN_ON(args.args_count != 1))
+				return -EINVAL;
+			*dev_id = args.args[0];
+			break;
+		}
+		index++;
+	} while (!ret);
+
+	return ret;
+}
+
+int __weak iort_pmsi_get_dev_id(struct device *dev, u32 *dev_id)
+{
+	return -1;
+}
+
+static int its_pmsi_prepare(struct irq_domain *domain, struct device *dev,
+			    int nvec, msi_alloc_info_t *info)
+{
+	struct msi_domain_info *msi_info;
+	u32 dev_id;
+	int ret;
+
+	if (dev->of_node)
+		ret = of_pmsi_get_dev_id(domain, dev, &dev_id);
+	else
+		ret = iort_pmsi_get_dev_id(dev, &dev_id);
+	if (ret)
+		return ret;
+
+	/* ITS specific DeviceID, as the core ITS ignores dev. */
+	info->scratchpad[0].ul = dev_id;
+
+	/*
+	 * @domain->msi_domain_info->hwsize contains the size of the device
+	 * domain, but vector allocation happens one by one.
+	 */
+	msi_info = msi_get_domain_info(domain);
+	if (msi_info->hwsize > nvec)
+		nvec = msi_info->hwsize;
+
+	/* Allocate at least 32 MSIs, and always as a power of 2 */
+	nvec = max_t(int, 32, roundup_pow_of_two(nvec));
+
+	msi_info = msi_get_domain_info(domain->parent);
+	return msi_info->ops->msi_prepare(domain->parent,
+					  dev, nvec, info);
+}
+
 static bool its_init_dev_msi_info(struct device *dev, struct irq_domain *domain,
 				  struct irq_domain *real_parent, struct msi_domain_info *info)
 {
@@ -117,6 +180,14 @@ static bool its_init_dev_msi_info(struct
 		 */
 		info->ops->msi_prepare = its_pci_msi_prepare;
 		break;
+	case DOMAIN_BUS_DEVICE_IMS:
+	case DOMAIN_BUS_WIRED_TO_MSI:
+		/*
+		 * FIXME: See the above PCI prepare comment. The domain
+		 * size is also known at domain creation time.
+		 */
+		info->ops->msi_prepare = its_pmsi_prepare;
+		break;
 	default:
 		/* Confused. How did the lib return true? */
 		WARN_ON_ONCE(1);
@@ -130,7 +201,7 @@ const struct msi_parent_ops gic_v3_its_m
 	.supported_flags	= ITS_MSI_FLAGS_SUPPORTED,
 	.required_flags		= ITS_MSI_FLAGS_REQUIRED,
 	.bus_select_token	= DOMAIN_BUS_NEXUS,
-	.bus_select_mask	= MATCH_PCI_MSI,
+	.bus_select_mask	= MATCH_PCI_MSI | MATCH_PLATFORM_MSI,
 	.prefix			= "ITS-",
 	.init_dev_msi_info	= its_init_dev_msi_info,
 };
--- a/drivers/irqchip/irq-gic-v3-its-platform-msi.c
+++ /dev/null
@@ -1,163 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Copyright (C) 2013-2015 ARM Limited, All Rights Reserved.
- * Author: Marc Zyngier <marc.zyngier@arm.com>
- */
-
-#include <linux/acpi_iort.h>
-#include <linux/device.h>
-#include <linux/msi.h>
-#include <linux/of.h>
-#include <linux/of_irq.h>
-
-static struct irq_chip its_pmsi_irq_chip = {
-	.name			= "ITS-pMSI",
-};
-
-static int of_pmsi_get_dev_id(struct irq_domain *domain, struct device *dev,
-				  u32 *dev_id)
-{
-	int ret, index = 0;
-
-	/* Suck the DeviceID out of the msi-parent property */
-	do {
-		struct of_phandle_args args;
-
-		ret = of_parse_phandle_with_args(dev->of_node,
-						 "msi-parent", "#msi-cells",
-						 index, &args);
-		if (args.np == irq_domain_get_of_node(domain)) {
-			if (WARN_ON(args.args_count != 1))
-				return -EINVAL;
-			*dev_id = args.args[0];
-			break;
-		}
-		index++;
-	} while (!ret);
-
-	return ret;
-}
-
-int __weak iort_pmsi_get_dev_id(struct device *dev, u32 *dev_id)
-{
-	return -1;
-}
-
-static int its_pmsi_prepare(struct irq_domain *domain, struct device *dev,
-			    int nvec, msi_alloc_info_t *info)
-{
-	struct msi_domain_info *msi_info;
-	u32 dev_id;
-	int ret;
-
-	msi_info = msi_get_domain_info(domain->parent);
-
-	if (dev->of_node)
-		ret = of_pmsi_get_dev_id(domain, dev, &dev_id);
-	else
-		ret = iort_pmsi_get_dev_id(dev, &dev_id);
-	if (ret)
-		return ret;
-
-	/* ITS specific DeviceID, as the core ITS ignores dev. */
-	info->scratchpad[0].ul = dev_id;
-
-	/* Allocate at least 32 MSIs, and always as a power of 2 */
-	nvec = max_t(int, 32, roundup_pow_of_two(nvec));
-	return msi_info->ops->msi_prepare(domain->parent,
-					  dev, nvec, info);
-}
-
-static struct msi_domain_ops its_pmsi_ops = {
-	.msi_prepare	= its_pmsi_prepare,
-};
-
-static struct msi_domain_info its_pmsi_domain_info = {
-	.flags	= (MSI_FLAG_USE_DEF_DOM_OPS | MSI_FLAG_USE_DEF_CHIP_OPS),
-	.ops	= &its_pmsi_ops,
-	.chip	= &its_pmsi_irq_chip,
-};
-
-static const struct of_device_id its_device_id[] = {
-	{	.compatible	= "arm,gic-v3-its",	},
-	{},
-};
-
-static int __init its_pmsi_init_one(struct fwnode_handle *fwnode,
-				const char *name)
-{
-	struct irq_domain *parent;
-
-	parent = irq_find_matching_fwnode(fwnode, DOMAIN_BUS_NEXUS);
-	if (!parent || !msi_get_domain_info(parent)) {
-		pr_err("%s: unable to locate ITS domain\n", name);
-		return -ENXIO;
-	}
-
-	if (!platform_msi_create_irq_domain(fwnode, &its_pmsi_domain_info,
-					    parent)) {
-		pr_err("%s: unable to create platform domain\n", name);
-		return -ENXIO;
-	}
-
-	pr_info("Platform MSI: %s domain created\n", name);
-	return 0;
-}
-
-#ifdef CONFIG_ACPI
-static int __init
-its_pmsi_parse_madt(union acpi_subtable_headers *header,
-			const unsigned long end)
-{
-	struct acpi_madt_generic_translator *its_entry;
-	struct fwnode_handle *domain_handle;
-	const char *node_name;
-	int err = -ENXIO;
-
-	its_entry = (struct acpi_madt_generic_translator *)header;
-	node_name = kasprintf(GFP_KERNEL, "ITS@0x%lx",
-			      (long)its_entry->base_address);
-	domain_handle = iort_find_domain_token(its_entry->translation_id);
-	if (!domain_handle) {
-		pr_err("%s: Unable to locate ITS domain handle\n", node_name);
-		goto out;
-	}
-
-	err = its_pmsi_init_one(domain_handle, node_name);
-
-out:
-	kfree(node_name);
-	return err;
-}
-
-static void __init its_pmsi_acpi_init(void)
-{
-	acpi_table_parse_madt(ACPI_MADT_TYPE_GENERIC_TRANSLATOR,
-			      its_pmsi_parse_madt, 0);
-}
-#else
-static inline void its_pmsi_acpi_init(void) { }
-#endif
-
-static void __init its_pmsi_of_init(void)
-{
-	struct device_node *np;
-
-	for (np = of_find_matching_node(NULL, its_device_id); np;
-	     np = of_find_matching_node(np, its_device_id)) {
-		if (!of_device_is_available(np))
-			continue;
-		if (!of_property_read_bool(np, "msi-controller"))
-			continue;
-
-		its_pmsi_init_one(of_node_to_fwnode(np), np->full_name);
-	}
-}
-
-static int __init its_pmsi_init(void)
-{
-	its_pmsi_of_init();
-	its_pmsi_acpi_init();
-	return 0;
-}
-early_initcall(its_pmsi_init);
