video: add of helper for display timings/videomode

video: add of helper for display timings/videomode

This adds support for reading display timings from DT into a struct
display_timings. The of_display_timing implementation supports multiple
subnodes. All children are read into an array, that can be queried.

If no native mode is specified, the first subnode will be used.

For cases where the graphics driver knows there can be only one
mode description or where the driver only supports one mode, a helper
function of_get_videomode is added, that gets a struct videomode from DT.

Signed-off-by: Steffen Trumtrar <[email protected]>
Signed-off-by: Philipp Zabel <[email protected]>
Acked-by: Stephen Warren <[email protected]>
Reviewed-by: Thierry Reding <[email protected]>
Acked-by: Thierry Reding <[email protected]>
Tested-by: Thierry Reding <[email protected]>
Tested-by: Philipp Zabel <[email protected]>
Reviewed-by: Laurent Pinchart <[email protected]>
Acked-by: Laurent Pinchart <[email protected]>
Tested-by: Afzal Mohammed <[email protected]>
Tested-by: Rob Clark <[email protected]>
Tested-by: Leela Krishna Amudala <[email protected]>