[POWERPC] Add irq_create_direct_mapping()

This patch adds irq_create_direct_mapping().  This routine is
an alternative to irq_create_mapping(), for irq controllers that
can use linux virq numbers directly as hardware numbers.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/include/asm-powerpc/irq.h b/include/asm-powerpc/irq.h
index 05dd5a3..0485c53 100644
--- a/include/asm-powerpc/irq.h
+++ b/include/asm-powerpc/irq.h
@@ -223,6 +223,15 @@
 extern unsigned int irq_find_mapping(struct irq_host *host,
 				     irq_hw_number_t hwirq);
 
+/**
+ * irq_create_direct_mapping - Allocate a virq for direct mapping
+ * @host: host to allocate the virq for or NULL for default host
+ *
+ * This routine is used for irq controllers which can choose the hardware
+ * interrupt numbers they generate. In such a case it's simplest to use
+ * the linux virq as the hardware interrupt number.
+ */
+extern unsigned int irq_create_direct_mapping(struct irq_host *host);
 
 /**
  * irq_radix_revmap - Find a linux virq from a hw irq number.