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>

1 files changed, 124 insertions, 0 deletions

diff --git a/Documentation/Makefile b/Documentation/Makefile
new file mode 100644
index 0000000000..2ca77ad0f2
--- /dev/null
+++ b/Documentation/Makefile
@@ -0,0 +1,124 @@
+# -*- makefile -*-
+# Makefile for Sphinx documentation
+#
+
+subdir-y :=
+
+# You can set these variables from the command line.
+SPHINXBUILD   = sphinx-build
+SPHINXOPTS    =
+SPHINXDIRS    = .
+_SPHINXDIRS   = $(patsubst $(srctree)/Documentation/%/conf.py,%,$(wildcard $(srctree)/Documentation/*/conf.py))
+SPHINX_CONF   = conf.py
+PAPER         =
+BUILDDIR      = $(obj)/output
+PDFLATEX      = xelatex
+LATEXOPTS     = -interaction=batchmode
+
+# User-friendly check for sphinx-build
+HAVE_SPHINX := $(shell if which $(SPHINXBUILD) >/dev/null 2>&1; then echo 1; else echo 0; fi)
+
+ifeq ($(HAVE_SPHINX),0)
+
+.DEFAULT:
+	$(warning The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed and in PATH, or set the SPHINXBUILD make variable to point to the full path of the '$(SPHINXBUILD)' executable.)
+	@echo
+	@./scripts/sphinx-pre-install
+	@echo "  SKIP    Sphinx $@ target."
+
+else # HAVE_SPHINX
+
+# User-friendly check for pdflatex
+HAVE_PDFLATEX := $(shell if which $(PDFLATEX) >/dev/null 2>&1; then echo 1; else echo 0; fi)
+
+# Internal variables.
+PAPEROPT_a4     = -D latex_paper_size=a4
+PAPEROPT_letter = -D latex_paper_size=letter
+KERNELDOC       = $(srctree)/scripts/kernel-doc
+KERNELDOC_CONF  = -D kerneldoc_srctree=$(srctree) -D kerneldoc_bin=$(KERNELDOC)
+ALLSPHINXOPTS   =  $(KERNELDOC_CONF) $(PAPEROPT_$(PAPER)) $(SPHINXOPTS)
+# the i18n builder cannot share the environment and doctrees with the others
+I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
+
+# commands; the 'cmd' from scripts/Kbuild.include is not *loopable*
+loop_cmd = $(echo-cmd) $(cmd_$(1)) || exit;
+
+# $2 sphinx builder e.g. "html"
+# $3 name of the build subfolder / e.g. "media", used as:
+#    * dest folder relative to $(BUILDDIR) and
+#    * cache folder relative to $(BUILDDIR)/.doctrees
+# $4 dest subfolder e.g. "man" for man pages at media/man
+# $5 reST source folder relative to $(srctree)/$(src),
+#    e.g. "media" for the linux-tv book-set at ./Documentation/media
+
+quiet_cmd_sphinx = SPHINX  $@ --> file://$(abspath $(BUILDDIR)/$3/$4)
+      cmd_sphinx = $(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/media $2 && \
+	PYTHONDONTWRITEBYTECODE=1 \
+	BUILDDIR=$(abspath $(BUILDDIR)) SPHINX_CONF=$(abspath $(srctree)/$(src)/$5/$(SPHINX_CONF)) \
+	$(SPHINXBUILD) \
+	-b $2 \
+	-c $(abspath $(srctree)/$(src)) \
+	-d $(abspath $(BUILDDIR)/.doctrees/$3) \
+	-D version=$(KERNELVERSION) -D release=$(KERNELRELEASE) \
+	$(ALLSPHINXOPTS) \
+	$(abspath $(srctree)/$(src)/$5) \
+	$(abspath $(BUILDDIR)/$3/$4)
+
+htmldocs:
+	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,html,$(var),,$(var)))
+
+linkcheckdocs:
+	@$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,linkcheck,$(var),,$(var)))
+
+latexdocs:
+	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,latex,$(var),latex,$(var)))
+
+ifeq ($(HAVE_PDFLATEX),0)
+
+pdfdocs:
+	$(warning The '$(PDFLATEX)' command was not found. Make sure you have it installed and in PATH to produce PDF output.)
+	@echo "  SKIP    Sphinx $@ target."
+
+else # HAVE_PDFLATEX
+
+pdfdocs: latexdocs
+	$(foreach var,$(SPHINXDIRS), $(MAKE) PDFLATEX=$(PDFLATEX) LATEXOPTS="$(LATEXOPTS)" -C $(BUILDDIR)/$(var)/latex || exit;)
+
+endif # HAVE_PDFLATEX
+
+epubdocs:
+	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,epub,$(var),epub,$(var)))
+
+xmldocs:
+	@+$(foreach var,$(SPHINXDIRS),$(call loop_cmd,sphinx,xml,$(var),xml,$(var)))
+
+endif # HAVE_SPHINX
+
+# The following targets are independent of HAVE_SPHINX, and the rules should
+# work or silently pass without Sphinx.
+
+refcheckdocs:
+	$(Q)cd $(srctree);scripts/documentation-file-ref-check
+
+cleandocs:
+	$(Q)rm -rf $(BUILDDIR)
+	$(Q)$(MAKE) BUILDDIR=$(abspath $(BUILDDIR)) $(build)=Documentation/media clean
+
+dochelp:
+	@echo  ' Linux kernel internal documentation in different formats from ReST:'
+	@echo  '  htmldocs        - HTML'
+	@echo  '  latexdocs       - LaTeX'
+	@echo  '  pdfdocs         - PDF'
+	@echo  '  epubdocs        - EPUB'
+	@echo  '  xmldocs         - XML'
+	@echo  '  linkcheckdocs   - check for broken external links (will connect to external hosts)'
+	@echo  '  refcheckdocs    - check for references to non-existing files under Documentation'
+	@echo  '  cleandocs       - clean all generated files'
+	@echo
+	@echo  '  make SPHINXDIRS="s1 s2" [target] Generate only docs of folder s1, s2'
+	@echo  '  valid values for SPHINXDIRS are: $(_SPHINXDIRS)'
+	@echo
+	@echo  '  make SPHINX_CONF={conf-file} [target] use *additional* sphinx-build'
+	@echo  '  configuration. This is e.g. useful to build with nit-picking config.'
+	@echo
+	@echo  '  Default location for the generated documents is Documentation/output'