Documentation: state: add unit name to state variable in DT ...

Starting with DT compiler version 1.4.6 (included since v2018.07.0) one gets
warnings

  <node>: node has a reg or ranges property, but no unit name

if the first address field of a reg-property is not taken as the unit name for
its parent node.

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Documentation: state: fix typos ...

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Documentation: state: harmonize capitalization in headings ...

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Documentation: state: mention SD/eMMC devices ...

The state framework also has support for SD/eMMC devices, so mention
them in the documentation.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

docs: rework and extend the 'state' and 'bootchooser' documentation ...

Many links between sections and examples were added to give the developer
the help to get it work.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

state: Update documentation ...

- explain what buckets are
- rework text about storage backends
- explain redundancy concept

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

boot: add framework for redundant boot scenarios ...

There are several use cases where a redundant Linux system is needed. The
barebox bootchooser framework provides the building blocks to model different
use cases without the need to start from the scratch over and over again.

The bootchooser works on abstract boot targets, each with a set of properties
and implements an algorithm which selects the highest priority target to boot.

See the documentation contained in this patch for more information.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

docs: Add/Update state documentation ...

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>