[PATCH] Add kernel<->userspace ABI stability documentation

Signed-off-by: Kay Sievers <kay.sievers@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/ABI/testing/sysfs-class

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+What:		/sys/class/
+Date:		Febuary 2006
+Contact:	Greg Kroah-Hartman <gregkh@suse.de>
+Description:
+		The /sys/class directory will consist of a group of
+		subdirectories describing individual classes of devices
+		in the kernel.  The individual directories will consist
+		of either subdirectories, or symlinks to other
+		directories.
+
+		All programs that use this directory tree must be able
+		to handle both subdirectories or symlinks in order to
+		work properly.
+
+Users:
+	udev <linux-hotplug-devel@lists.sourceforge.net>

Documentation/ABI/testing/sysfs-devices

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+What:		/sys/devices
+Date:		February 2006
+Contact:	Greg Kroah-Hartman <gregkh@suse.de>
+Description:
+		The /sys/devices tree contains a snapshot of the
+		internal state of the kernel device tree.  Devices will
+		be added and removed dynamically as the machine runs,
+		and between different kernel versions, the layout of the
+		devices within this tree will change.
+
+		Please do not rely on the format of this tree because of
+		this.  If a program wishes to find different things in
+		the tree, please use the /sys/class structure and rely
+		on the symlinks there to point to the proper location
+		within the /sys/devices tree of the individual devices.
+		Or rely on the uevent messages to notify programs of
+		devices being added and removed from this tree to find
+		the location of those devices.
+
+		Note that sometimes not all devices along the directory
+		chain will have emitted uevent messages, so userspace
+		programs must be able to handle such occurrences.
+
+Users:
+	udev <linux-hotplug-devel@lists.sourceforge.net>