drm: Introduce generic probe function for component based masters.

A lot of component based DRM drivers use a variant of the same code
as the probe function. They bind the crtc ports in the first iteration
and then scan through the child nodes and bind the encoders attached
to the remote endpoints. Factor the common code into a separate
function called drm_of_component_probe() in order to increase code
reuse.

Cc: David Airlie <airlied@linux.ie>
Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1445332995-11212-2-git-send-email-Liviu.Dudau@arm.com
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index 2441f71..8544665 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -1,18 +1,31 @@
 #ifndef __DRM_OF_H__
 #define __DRM_OF_H__
 
+struct component_master_ops;
+struct device;
 struct drm_device;
 struct device_node;
 
 #ifdef CONFIG_OF
 extern uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 					   struct device_node *port);
+extern int drm_of_component_probe(struct device *dev,
+				  int (*compare_of)(struct device *, void *),
+				  const struct component_master_ops *m_ops);
 #else
 static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 						  struct device_node *port)
 {
 	return 0;
 }
+
+static inline int
+drm_of_component_probe(struct device *dev,
+		       int (*compare_of)(struct device *, void *),
+		       const struct component_master_ops *m_ops)
+{
+	return -EINVAL;
+}
 #endif
 
 #endif /* __DRM_OF_H__ */