doc/efi: add load file 2 protocol to HTML documentation

The load file 2 protocol can be used by the Linux kernel to load the initial
RAM disk. U-Boot can be configured to provide an implementation.

Add a description to the UEFI overview and document the related functions
in the API section.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/doc/uefi/uefi.rst b/doc/uefi/uefi.rst
index a8fd886..cfe2d84 100644
--- a/doc/uefi/uefi.rst
+++ b/doc/uefi/uefi.rst
@@ -356,6 +356,18 @@
     CONFIG_BLK=y
     CONFIG_PARTITIONS=y
 
+Miscellaneous
+-------------
+
+Load file 2 protocol
+~~~~~~~~~~~~~~~~~~~~
+
+The load file 2 protocol can be used by the Linux kernel to load the initial
+RAM disk. U-Boot can be configured to provide an implementation with::
+
+    EFI_LOAD_FILE2_INITRD=y
+    EFI_INITRD_FILESPEC=interface dev:part path_to_initrd
+
 Links
 -----