of/platform: Assign MSI domain to platform device

As for PCI, we're able to populate the msi_domain field at probe time,
provided that the device tree has an "msi-parent" property.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: Yijing Wang <wangyijing@huawei.com>
Cc: Ma Jun <majun258@huawei.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Duc Dang <dhdang@apm.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Jason Cooper <jason@lakedaemon.net>
Link: http://lkml.kernel.org/r/1438091186-10244-9-git-send-email-marc.zyngier@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/of/irq.c

@@ -18,6 +18,7 @@
  * driver.
  */
 
+#include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/list.h>
 #include <linux/module.h>
@@ -576,3 +577,23 @@ err:
 		kfree(desc);
 	}
 }
+
+/**
+ * of_msi_configure - Set the msi_domain field of a device
+ * @dev: device structure to associate with an MSI irq domain
+ * @np: device node for that device
+ */
+void of_msi_configure(struct device *dev, struct device_node *np)
+{
+	struct device_node *msi_np;
+	struct irq_domain *d;
+
+	msi_np = of_parse_phandle(np, "msi-parent", 0);
+	if (!msi_np)
+		return;
+
+	d = irq_find_matching_host(msi_np, DOMAIN_BUS_PLATFORM_MSI);
+	if (!d)
+		d = irq_find_host(msi_np);
+	dev_set_msi_domain(dev, d);
+}