doc: Replace DocBook with sphinx-based docs

The Linux kernel moved to sphinx-based documentation and got rid of the
DocBook based documentation quite a while ago. Hence, the DocBook
documentation for U-Boot should be converted as well.

To achieve this, import the necessary files from Linux v4.17, and
convert the current DocBook documentation (three files altogether) to
sphinx/reStructuredText.

For now, all old DocBook documentation was merged into a single
handbook, tentatively named "U-Boot Hacker Manual".

For some source files, the documentation style was changed to comply
with kernel-doc; no functional changes were applied.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/Documentation/media/Makefile b/Documentation/media/Makefile
new file mode 100644
index 0000000..0efd18a
--- /dev/null
+++ b/Documentation/media/Makefile
@@ -0,0 +1,38 @@
+# Rules to convert a .h file to inline RST documentation
+
+SRC_DIR=$(srctree)/Documentation/media
+PARSER = $(srctree)/Documentation/sphinx/parse-headers.pl
+API = $(srctree)/include
+
+FILES = linker_lists.h.rst
+
+TARGETS := $(addprefix $(BUILDDIR)/, $(FILES))
+
+gen_rst = \
+	echo ${PARSER} $< $@ $(SRC_DIR)/$(notdir $@).exceptions; \
+	${PARSER} $< $@ $(SRC_DIR)/$(notdir $@).exceptions
+
+quiet_gen_rst = echo '  PARSE   $(patsubst $(srctree)/%,%,$<)'; \
+	${PARSER} $< $@ $(SRC_DIR)/$(notdir $@).exceptions
+
+silent_gen_rst = ${gen_rst}
+
+$(BUILDDIR)/linker_lists.h.rst: ${API}/linker_lists.h ${PARSER} $(SRC_DIR)/linker_lists.h.rst.exceptions
+	@$($(quiet)gen_rst)
+
+# Media build rules
+
+.PHONY: all html epub xml latex
+
+all: $(IMGDOT) $(BUILDDIR) ${TARGETS}
+html: all
+epub: all
+xml: all
+latex: $(IMGPDF) all
+linkcheck:
+
+clean:
+	-rm -f $(DOTTGT) $(IMGTGT) ${TARGETS} 2>/dev/null
+
+$(BUILDDIR):
+	$(Q)mkdir -p $@