drivers: video: add a struct video_dt_spec and C macro

This introduces a video_dt_spec that can be used by the APIs to refer
one particular video endpoint out of a video device and refer it in
one go.

Signed-off-by: Josuah Demangeon <[email protected]>

include/zephyr/drivers/video.h

@@ -33,6 +33,42 @@
 extern "C" {
 #endif
 
+/**
+ * @brief Video Device Tree endpoint identifier
+ *
+ * Identify a particular port and particular endpoint of a video device,
+ * providing all the context necessary to act upon a video device, via one of
+ * its endpoint.
+ */
+struct video_dt_spec {
+	/** Device instance of the remote video device to communicate with. */
+	const struct device *dev;
+	/** Devicetree address for this endpoint. */
+	uint32_t endpoint;
+};
+
+/**
+ * @brief Get a device reference for an endpoint of a video controller.
+ *
+ * @code
+ * mipi0: mipi-controller@... {
+ *     mipi0out: endpoint@0 {
+ *         remote-endpoint = <&mjpeg0in>;
+ *     };
+ * };
+ * @endcode
+ *
+ * Here, the devicetree spec for mipi0out can be obtaine with:
+ *
+ * @code
+ * struct video_dt_spec spec = VIDEO_DT_SPEC_GET(DT_NODELABEL(mipi0out));
+ * @endcode
+ *
+ * @param node_id node identifier of an endpoint phandle property
+ */
+#define VIDEO_DT_SPEC_GET(node_id)                                                                 \
+	{.dev = DEVICE_DT_GET(DT_BUS(node_id)), .endpoint = VIDEO_ENDPOINT_ID(node_id)}
+
 /**
  * Obtain the endpoint ID out of an devicetree endpoint node.
  *