x86: dtb: Add irq domain abstraction

The here introduced irq_domain abstraction represents a generic irq
controller. It is a subset of powerpc's irq_host which is going to be
renamed to irq_domain and then become generic. This implementation will
be removed once it is generic.

The xlate callback is resposible to parse irq informations like irq type
and number and returns the hardware irq number which is reported by the
hardware as active.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: sodaville@linutronix.de
Cc: devicetree-discuss@lists.ozlabs.org
LKML-Reference: <1298405266-1624-5-git-send-email-bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/prom.h

@@ -20,9 +20,11 @@
 #include <asm/irq.h>
 #include <asm/atomic.h>
 #include <asm/setup.h>
+#include <asm/irq_controller.h>
 
 #ifdef CONFIG_OF
 extern void add_dtb(u64 data);
+void add_interrupt_host(struct irq_domain *ih);
 #else
 static inline void add_dtb(u64 data) { }
 #endif