ARM: DT: Enable symbols when CONFIG_OF_OVERLAY is used
of: overlay: Do not generate duplicate nodes

During the course of the rewrites a bug sneaked in when dealing
with children nodes of overlays, which ends up duplicating
sub nodes.

Simply remove the duplicate traversal of child nodes to fix.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
of: platform: Handle of_populate drivers in notifier

When using overlays with drivers calling of_populate the notifier
will try to create the device twice. Using the populated bit
before proceeding protects against this.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
of: unittest: Overlays with sub-devices tests

Introduce selftests for overlays using sub-devices present
in children nodes.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
[RFC] OF: probe order dependency aware of_platform_populate

A nice side-effect of the changes in DTC for supporting overlays
is that it is now possible to do dependency tracking of platform
devices automatically.

This patch implements dependency aware probe order for users
of of_platform_populate.

There are no changes in the syntax of the DTS bindings, the
dependency is generated automatically by the use of phandle
references.

Signed-off-by: Pantelis Antoniou <pantelis.antoniou@konsulko.com>
WIP unittest