Provide a man-page for the md command.

Signed-off-by: Simon Glass <sjg@chromium.org>

Update the help message used for 'make help':

  Documentation targets:
    Linux kernel internal documentation in different formats from ReST:
=>
    U-Boot documentation in different formats from ReST:

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Several patches delivered incorrect restructured text as documentation. We
should be able to discover this in Travis CI, Gitlab CI, or Azure CI.

So let us turn all build warnings into errors.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

Commit ad7061ed742e ("doc: Move device tree bindings documentation to
 doc/device-tree-bindings") moved all device tree binding documentation
to doc/device-tree-bindings directory.

The current U-Boot project still have two documentation directories:

- doc/
- Documentation/

Move all documentation and sphinx files to doc directory so all content
can be in a common place.

Signed-off-by: Breno Lima <breno.lima@nxp.com>