doc: add structure to Sphinx generated docs

Create separate html pages for linker lists, the serial subsystem,
and the EFI subsystem.

Add a table of content.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/MAINTAINERS b/MAINTAINERS
index 58b61ac..8a2f0a7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -364,9 +364,9 @@
 M:	Alexander Graf <agraf@suse.de>
 S:	Maintained
 T:	git git://github.com/agraf/u-boot.git
-F:	doc/DocBook/efi.tmpl
 F:	doc/README.uefi
 F:	doc/README.iscsi
+F:	Documentation/efi.rst
 F:	include/efi*
 F:	include/pe.h
 F:	include/asm-generic/pe.h