xtensa: allow variant to initialize own irq chips

There was already a PLATFORM_NR_IRQS define, which is now accompanied
by a VARIANT_NR_IRQS. To be able to initialize these interrupts,
init_IRQ now calls a variant specific hook.

Changes compared to v1:
- adapted to new CONFIG_VARIANT_IRQ_EXT
- removed definition and call of platform_init_IRQ as there already
  is a platform_init_irq defined in asm/platform.h with a weak default
  in kernel/platform.c
- renamed variant_init_IRQ to variant_init_irq

Note that I could not find the call site of platform_init_irq although
it is stated in platform.h that it is called from init_IRQ.
Signed-off-by: Daniel Glöckner <dg@emlix.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/include/asm/irq.h

@@ -11,6 +11,7 @@
 #ifndef _XTENSA_IRQ_H
 #define _XTENSA_IRQ_H
 
+#include <linux/init.h>
 #include <platform/hardware.h>
 #include <variant/core.h>
 
@@ -21,11 +22,20 @@ static inline void variant_irq_enable(unsigned int irq) { }
 static inline void variant_irq_disable(unsigned int irq) { }
 #endif
 
+#ifndef VARIANT_NR_IRQS
+# define VARIANT_NR_IRQS 0
+#endif
 #ifndef PLATFORM_NR_IRQS
 # define PLATFORM_NR_IRQS 0
 #endif
 #define XTENSA_NR_IRQS XCHAL_NUM_INTERRUPTS
-#define NR_IRQS (XTENSA_NR_IRQS + PLATFORM_NR_IRQS)
+#define NR_IRQS (XTENSA_NR_IRQS + VARIANT_NR_IRQS + PLATFORM_NR_IRQS)
+
+#if VARIANT_NR_IRQS == 0
+static inline void variant_init_irq(void) { }
+#else
+void variant_init_irq(void) __init;
+#endif
 
 static __inline__ int irq_canonicalize(int irq)
 {

arch/xtensa/kernel/irq.c

@@ -197,4 +197,6 @@ void __init init_IRQ(void)
 	}
 
 	cached_irq_mask = 0;
+
+	variant_init_irq();
 }