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Adding an overview of DRRS in general and the implementation for eDP DRRS.
Also, describing the functions related to eDP DRRS.
Signed-off-by: Vandana Kannan <vandana.kannan@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>