irqdomain: Let irq_find_host default to DOMAIN_BUS_WIRED

At the beginning of times, irq_find_host() was simple. Each device node
implemented at most one irq domain, and we were happy. Over time, things
have become more complex, and we now have nodes implementing a plurality
of domains, tagged by "bus_token".

Crutially, users of irq_find_host() all expect the most basic domain
to be returned, and not any other domain such as a bus-specific MSI
domain.

So let's change irq_find_host() to first look for a DOMAIN_BUS_WIRED
domain, and only if this fails fallback to DOMAIN_BUS_ANY. Note that
this is consistent with what irq_create_fwspec_mapping is already
doing, see 530cbe1 ("irqdomain: Allow domain lookup with
DOMAIN_BUS_WIRED token").

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lkml.kernel.org/r/20180508121438.11301-6-marc.zyngier@arm.com

include/linux/irqdomain.h

@@ -301,7 +301,13 @@ static inline struct irq_domain *irq_find_matching_host(struct device_node *node
 
 static inline struct irq_domain *irq_find_host(struct device_node *node)
 {
-	return irq_find_matching_host(node, DOMAIN_BUS_ANY);
+	struct irq_domain *d;
+
+	d = irq_find_matching_host(node, DOMAIN_BUS_WIRED);
+	if (!d)
+		d = irq_find_matching_host(node, DOMAIN_BUS_ANY);
+
+	return d;
 }
 
 /**