of/irq: Use the msi-map property to provide device-specific MSI domain

While msi-parent is used to point to the MSI controller that
works for all the devices behind a root complex, it doesn't
allow configurations where each individual device can be routed
to a separate MSI controller.

The msi-map property provides this flexibility (and much more),
so let's add a utility function that parses it, and return the
corresponding MSI domain.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

include/linux/of_irq.h

@@ -49,6 +49,8 @@ extern int of_irq_to_resource_table(struct device_node *dev,
 extern struct irq_domain *of_msi_get_domain(struct device *dev,
 					    struct device_node *np,
 					    enum irq_domain_bus_token token);
+extern struct irq_domain *of_msi_map_get_device_domain(struct device *dev,
+						       u32 rid);
 #else
 static inline int of_irq_count(struct device_node *dev)
 {
@@ -73,6 +75,11 @@ static inline struct irq_domain *of_msi_get_domain(struct device *dev,
 {
 	return NULL;
 }
+static inline struct irq_domain *of_msi_map_get_device_domain(struct device *dev,
+							      u32 rid)
+{
+	return NULL;
+}
 #endif
 
 #if defined(CONFIG_OF)