[ARM] 3690/1: genirq: Introduce and make use of dummy irq chip

Patch from Thomas Gleixner

From: Thomas Gleixner <tglx@linutronix.de>

ARM has a couple of really dumb interrupt controllers.
Implement a generic one and fixup the ARM migration. ARM reused
the no_irq_chip for this purpose, but this does not work out
for platforms which are not converted to the new interrupt
type handling model.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 0832149..00b6ef8 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -348,8 +348,9 @@
 /* Checks whether the interrupt can be requested by request_irq(): */
 extern int can_request_irq(unsigned int irq, unsigned long irqflags);
 
-/* Dummy irq-chip implementation: */
+/* Dummy irq-chip implementations: */
 extern struct irq_chip no_irq_chip;
+extern struct irq_chip dummy_irq_chip;
 
 extern void
 set_irq_chip_and_handler(unsigned int irq, struct irq_chip *chip,