irq_domain: add documentation and MAINTAINERS entry.

Documentation for irq_domain library which will be created in subsequent
patches.

v4: editorial changes

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Reviewed-by: Randy Dunlap <rdunlap@xenotime.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Milton Miller <miltonm@bga.com>
Tested-by: Olof Johansson <olof@lixom.net>
diff --git a/MAINTAINERS b/MAINTAINERS
index 9a648eb..57dd0f5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3640,6 +3640,15 @@
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git irq/core
 F:	kernel/irq/
 
+IRQ DOMAINS (IRQ NUMBER MAPPING LIBRARY)
+M:	Benjamin Herrenschmidt <benh@kernel.crashing.org>
+M:	Grant Likely <grant.likely@secretlab.ca>
+T:	git git://git.secretlab.ca/git/linux-2.6.git irqdomain/next
+S:	Maintained
+F:	Documentation/IRQ-domain.txt
+F:	include/linux/irqdomain.h
+F:	kernel/irq/irqdomain.c
+
 ISAPNP
 M:	Jaroslav Kysela <perex@perex.cz>
 S:	Maintained