documentation: networking: add 6lowpan documentation

This patch adds a 6lowpan.txt into the networking documentation
directory. Currently this documentation describes how the lowpan
private data of net devices will be handled.

Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Suggested-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/MAINTAINERS b/MAINTAINERS
index 98ede02..5baa91c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -158,6 +158,7 @@
 S:	Maintained
 F:	net/6lowpan/
 F:	include/net/6lowpan.h
+F:	Documentation/networking/6lowpan.txt
 
 6PACK NETWORK DRIVER FOR AX.25
 M:	Andreas Koensgen <ajk@comnets.uni-bremen.de>