mei: docs: add hdcp documentation

1. Add a short ducumentation for MEI HDCP driver,
and fix DOC comments in drivers/misc/mei/hdcp/mei_hdcp.c
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/driver-api/mei/hdcp.rst

+.. SPDX-License-Identifier: GPL-2.0
+
+HDCP:
+=====
+
+ME FW as a security engine provides the capability for setting up
+HDCP2.2 protocol negotiation between the Intel graphics device and
+an HDC2.2 sink.
+
+ME FW prepares HDCP2.2 negotiation parameters, signs and encrypts them
+according the HDCP 2.2 spec. The Intel graphics sends the created blob
+to the HDCP2.2 sink.
+
+Similarly, the HDCP2.2 sink's response is transferred to ME FW
+for decryption and verification.
+
+Once all the steps of HDCP2.2 negotiation are completed,
+upon request ME FW will configure the port as authenticated and supply
+the HDCP encryption keys to Intel graphics hardware.
+
+
+mei_hdcp driver
+---------------
+.. kernel-doc:: drivers/misc/mei/hdcp/mei_hdcp.c
+    :doc: MEI_HDCP Client Driver
+
+mei_hdcp api
+------------
+
+.. kernel-doc:: drivers/misc/mei/hdcp/mei_hdcp.c
+    :functions:
+

Documentation/driver-api/mei/mei-client-bus.rst

@@ -164,4 +164,5 @@ MEI Client Bus Drivers
 .. toctree::
    :maxdepth: 2
 
+   hdcp
    nfc

drivers/misc/mei/hdcp/mei_hdcp.c

@@ -2,7 +2,7 @@
 /*
  * Copyright © 2019 Intel Corporation
  *
- * Mei_hdcp.c: HDCP client driver for mei bus
+ * mei_hdcp.c: HDCP client driver for mei bus
  *
  * Author:
  * Ramalingam C <ramalingam.c@intel.com>
@@ -11,12 +11,9 @@
 /**
  * DOC: MEI_HDCP Client Driver
  *
- * This is a client driver to the mei_bus to make the HDCP2.2 services of
- * ME FW available for the interested consumers like I915.
- *
- * This module will act as a translation layer between HDCP protocol
- * implementor(I915) and ME FW by translating HDCP2.2 authentication
- * messages to ME FW command payloads and vice versa.
+ * The mei_hdcp driver acts as a translation layer between HDCP 2.2
+ * protocol  implementer (I915) and ME FW by translating HDCP2.2
+ * negotiation messages to ME FW command payloads and vice versa.
  */
 
 #include <linux/module.h>