pinctrl: add kerneldoc for pinctrl_ops device tree functions

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/pinctrl/pinctrl.h

@@ -72,6 +72,15 @@ struct pinctrl_gpio_range {
  *	group selector @pins, and the size of the array in @num_pins
  * @pin_dbg_show: optional debugfs display hook that will provide per-device
  *	info for a certain pin in debugfs
+ * @dt_node_to_map: parse a device tree "pin configuration node", and create
+ *	mapping table entries for it. These are returned through the @map and
+ *	@num_maps output parameters. This function is optional, and may be
+ *	omitted for pinctrl drivers that do not support device tree.
+ * @dt_free_map: free mapping table entries created via @dt_node_to_map. The
+ *	top-level @map pointer must be freed, along with any dynamically
+ *	allocated members of the mapping table entries themselves. This
+ *	function is optional, and may be omitted for pinctrl drivers that do
+ *	not support device tree.
  */
 struct pinctrl_ops {
 	int (*get_groups_count) (struct pinctrl_dev *pctldev);