drm/dsi: Resolve MIPI DSI device from phandle

Add a function, of_find_mipi_dsi_device_by_node(), that can be used to
resolve a phandle to a MIPI DSI device.

Acked-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 061a792..ea0d982 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -163,6 +163,7 @@
 	return container_of(dev, struct mipi_dsi_device, dev);
 }
 
+struct mipi_dsi_device *of_find_mipi_dsi_device_by_node(struct device_node *np);
 int mipi_dsi_attach(struct mipi_dsi_device *dsi);
 int mipi_dsi_detach(struct mipi_dsi_device *dsi);
 int mipi_dsi_set_maximum_return_packet_size(struct mipi_dsi_device *dsi,