--- zzzz-none-000/linux-3.18.24/drivers/pci/of.c	2015-10-31 20:39:51.000000000 +0000
+++ rtl96-5690pro-762/linux-3.18.24/drivers/pci/of.c	2024-08-14 08:36:36.000000000 +0000
@@ -9,6 +9,7 @@
  * 2 of the License, or (at your option) any later version.
  */
 
+#include <linux/irqdomain.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/of.h>
@@ -59,3 +60,32 @@
 		return of_node_get(bus->bridge->parent->of_node);
 	return NULL;
 }
+
+struct irq_domain *pci_host_bridge_of_msi_domain(struct pci_bus *bus)
+{
+#ifdef CONFIG_IRQ_DOMAIN
+	struct device_node *np;
+	struct irq_domain *d;
+
+	if (!bus->dev.of_node)
+		return NULL;
+
+	/* Start looking for a phandle to an MSI controller. */
+	np = of_parse_phandle(bus->dev.of_node, "msi-parent", 0);
+
+	/*
+	 * If we don't have an msi-parent property, look for a domain
+	 * directly attached to the host bridge.
+	 */
+	if (!np)
+		np = bus->dev.of_node;
+
+	d = irq_find_matching_host(np, DOMAIN_BUS_PCI_MSI);
+	if (d)
+		return d;
+
+	return irq_find_host(np);
+#else
+	return NULL;
+#endif
+}