ubifs: Document sysfs nodes

Add documentation for the new sysfs nodes

 /sys/fs/ubifs/ubiX_Y/errors_magic
 /sys/fs/ubifs/ubiX_Y/errors_node
 /sys/fs/ubifs/ubiX_Y/errors_crc
Signed-off-by: Stefan Schaeckeler <sschaeck@cisco.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

Documentation/ABI/testing/sysfs-fs-ubifs

+What:		/sys/fs/ubifsX_Y/error_magic
+Date:		October 2021
+KernelVersion:	5.16
+Contact:	linux-mtd@lists.infradead.org
+Description:
+		Exposes magic errors: every node starts with a magic number.
+
+		This counter keeps track of the number of accesses of nodes
+		with a corrupted magic number.
+
+		The counter is reset to 0 with a remount.
+
+What:		/sys/fs/ubifsX_Y/error_node
+Date:		October 2021
+KernelVersion:	5.16
+Contact:	linux-mtd@lists.infradead.org
+Description:
+		Exposes node errors. Every node embeds its type.
+
+		This counter keeps track of the number of accesses of nodes
+		with a corrupted node type.
+
+		The counter is reset to 0 with a remount.
+
+What:		/sys/fs/ubifsX_Y/error_crc
+Date:		October 2021
+KernelVersion:	5.16
+Contact:	linux-mtd@lists.infradead.org
+Description:
+		Exposes crc errors: every node embeds a crc checksum.
+
+		This counter keeps track of the number of accesses of nodes
+		with a bad crc checksum.
+
+		The counter is reset to 0 with a remount.

MAINTAINERS

@@ -19444,6 +19444,7 @@ S:	Supported
 W:	http://www.linux-mtd.infradead.org/doc/ubifs.html
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs.git next
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rw/ubifs.git fixes
+F:	Documentation/ABI/testing/sysfs-fs-ubifs
 F:	Documentation/filesystems/ubifs-authentication.rst
 F:	Documentation/filesystems/ubifs.rst
 F:	fs/ubifs/