The davinci VPIF is a single hardware block, but the existing driver
is broken up into a common library (vpif.c), output (vpif_display.c) and
intput (vpif_capture.c).

When migrating to DT, to better model the hardware, and because
registers, interrupts, etc. are all common,it was decided to
have a single VPIF hardware node[1].

Because davinci uses legacy, non-DT boot on several SoCs still, the
platform_drivers need to remain.  But they are also needed in DT boot.
Since there are no DT nodes for the display/capture parts in DT
boot (there is a single node for the parent/common device) we need to
create platform_devices somewhere to instantiate the platform_drivers.

When VPIF display/capture are needed for a DT boot, the VPIF node
will have endpoints defined for its subdevs.  Therefore, vpif_probe()
checks for the presence of endpoints, and if detected manually creates
the platform_devices for the display and capture platform_drivers.

[1] Documentation/devicetree/bindings/media/ti,da850-vpif.txt
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>