We have previously added logic to allow a "fallback" option to be
specified in the extlinux configuration. Provide a command that allows
us to set this as the preferred default option when booting.

Combined with the bootcount functionality, this allows the "altbootcmd"
to provide a means of falling back to a previously known good state
after a failed update. For example, if "bootcmd" is set to:

    bootflow scan -lb

We would set "altbootcmd" to:

    bootmeth set extlinux fallback 1; bootflow scan -lb

Causing the boot process to boot from the fallback option.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

Before adding more files, move the bootstd docs into a new directory,
with an index.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>

Fix a trivial typo in the bootmeth documentation.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

%s/Synopis/Synopsis/g

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

Add the description of CLI commands to the generated index.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

We use the terms 'distro' to mean extlinux but they are not really the
same. 'Distro' could refer to any method of booting a distribution,
whereas extlinux is a particular method.

Also we sometimes use syslinux, but it is better to use the same term in
all cases.

Rename distro to syslinux and also update bootstd uses of syslinux to use
extlinux instead.

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

Add some documentation updates, particularly about global bootmeths.

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

Add documentation for this feature, including the commands and full
devicetree bindings.

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