Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/driver-api/md/index.rst b/Documentation/driver-api/md/index.rst
new file mode 100644
index 0000000..18f54a7
--- /dev/null
+++ b/Documentation/driver-api/md/index.rst
@@ -0,0 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====
+RAID
+====
+
+.. toctree::
+   :maxdepth: 1
+
+   md-cluster
+   raid5-cache
+   raid5-ppl