Now that Linux has accepted these tags, move U-Boot over to use them.
Tidy up the comments and formatting, making sure that VPL is mentioned
too.

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

In a couple of places the document says u-boot,pre-reloc but all
examples show u-boot,dm-pre-reloc, use the latter consistently.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

With the last platform for this architecture removed, remove the rest of
the architecture support as well.

Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

This is an attempt to cover the common cases found when enabling driver
model for serial on a new board.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

These docs are useful for developers, not users. Move them under that
section.

Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>