arm: add set_handle_irq() to register the parent IRQ controller handler function

In order to allow irqchip drivers to register their IRQ handling
function as the parent IRQ controller handler function, we provide a
convenience function. This will avoid poking directly into the global
handle_arch_irq variable.

Suggested by Arnd Bergmann.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Rob Herring: remove warning. 1st one to initialize wins.]
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Olof Johansson <olof@lixom.net>

arch/arm/include/asm/mach/irq.h

@@ -22,6 +22,7 @@ extern int show_fiq_list(struct seq_file *, int);
 
 #ifdef CONFIG_MULTI_IRQ_HANDLER
 extern void (*handle_arch_irq)(struct pt_regs *);
+extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 #endif
 
 /*

arch/arm/kernel/irq.c

@@ -117,6 +117,16 @@ void __init init_IRQ(void)
 	machine_desc->init_irq();
 }
 
+#ifdef CONFIG_MULTI_IRQ_HANDLER
+void __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
+{
+	if (handle_arch_irq)
+		return;
+
+	handle_arch_irq = handle_irq;
+}
+#endif
+
 #ifdef CONFIG_SPARSE_IRQ
 int __init arch_probe_nr_irqs(void)
 {