Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/Documentation/driver-api/firmware/other_interfaces.rst b/Documentation/driver-api/firmware/other_interfaces.rst
index 36c47b1..b81794e 100644
--- a/Documentation/driver-api/firmware/other_interfaces.rst
+++ b/Documentation/driver-api/firmware/other_interfaces.rst
@@ -13,3 +13,33 @@
 .. kernel-doc:: drivers/firmware/edd.c
    :internal:
 
+Intel Stratix10 SoC Service Layer
+---------------------------------
+Some features of the Intel Stratix10 SoC require a level of privilege
+higher than the kernel is granted. Such secure features include
+FPGA programming. In terms of the ARMv8 architecture, the kernel runs
+at Exception Level 1 (EL1), access to the features requires
+Exception Level 3 (EL3).
+
+The Intel Stratix10 SoC service layer provides an in kernel API for
+drivers to request access to the secure features. The requests are queued
+and processed one by one. ARM’s SMCCC is used to pass the execution
+of the requests on to a secure monitor (EL3).
+
+.. kernel-doc:: include/linux/firmware/intel/stratix10-svc-client.h
+   :functions: stratix10_svc_command_code
+
+.. kernel-doc:: include/linux/firmware/intel/stratix10-svc-client.h
+   :functions: stratix10_svc_client_msg
+
+.. kernel-doc:: include/linux/firmware/intel/stratix10-svc-client.h
+   :functions: stratix10_svc_command_config_type
+
+.. kernel-doc:: include/linux/firmware/intel/stratix10-svc-client.h
+   :functions: stratix10_svc_cb_data
+
+.. kernel-doc:: include/linux/firmware/intel/stratix10-svc-client.h
+   :functions: stratix10_svc_client
+
+.. kernel-doc:: drivers/firmware/stratix10-svc.c
+   :export: