irqchip/gic-v3-its: Add support for device tree msi-map and msi-mask

JIRA: https://issues.redhat.com/browse/RHEL-120705
Upstream Status: f1680d9

commit f1680d9
Author: Frank Li <Frank.Li@nxp.com>
Date:   Mon Apr 14 14:30:59 2025 -0400

    irqchip/gic-v3-its: Add support for device tree msi-map and msi-mask

    Some platform devices create child devices dynamically and require the
    parent device's msi-map to map device IDs to actual sideband information.

    A typical use case is using ITS as a PCIe Endpoint Controller(EPC)'s
    doorbell function, where PCI hosts send TLP memory writes to the EP
    controller. The EP controller converts these writes to AXI transactions
    and appends platform-specific sideband information.

    EPC's DTS will provide such information by msi-map and msi-mask. A
    simplified dts as

    pcie-ep@10000000 {
            ...
            msi-map = <0 &its 0xc 8>;
                              ^^^ 0xc is implement defined sideband information,
                                  which append to AXI write transaction.
                       ^ 0 is function index.

            msi-mask = <0x7>
    }

    Check msi-map if msi-parent missed to keep compatility with existing systems.

    Signed-off-by: Frank Li <Frank.Li@nxp.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Link: https://lore.kernel.org/all/20250414-ep-msi-v18-5-f69b49917464@nxp.com

Signed-off-by: Myron Stowe <mstowe@redhat.com>

Author: Myron Stowe

drivers/irqchip/irq-gic-v3-its-msi-parent.c

@@ -118,6 +118,14 @@ static int of_pmsi_get_dev_id(struct irq_domain *domain, struct device *dev,
 		index++;
 	} while (!ret);
 
+	if (ret) {
+		struct device_node *np = NULL;
+
+		ret = of_map_id(dev->of_node, dev->id, "msi-map", "msi-map-mask", &np, dev_id);
+		if (np)
+			of_node_put(np);
+	}
+
 	return ret;
 }