Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/spi/index.rst b/Documentation/spi/index.rst
new file mode 100644
index 0000000..06c34ea
--- /dev/null
+++ b/Documentation/spi/index.rst
@@ -0,0 +1,22 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================================
+Serial Peripheral Interface (SPI)
+=================================
+
+.. toctree::
+   :maxdepth: 1
+
+   spi-summary
+   spidev
+   butterfly
+   pxa2xx
+   spi-lm70llp
+   spi-sc18is602
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`