reset: improve of_xlate documentation

Mention of_reset_simple_xlate as the default if of_xlate is not set.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/reset/core.c

@@ -78,8 +78,10 @@ static const char *rcdev_name(struct reset_controller_dev *rcdev)
  * @reset_spec: reset line specifier as found in the device tree
  * @flags: a flags pointer to fill in (optional)
  *
- * This simple translation function should be used for reset controllers
- * with 1:1 mapping, where reset lines can be indexed by number without gaps.
+ * This static translation function is used by default if of_xlate in
+ * :c:type:`reset_controller_dev` is not set. It is useful for all reset
+ * controllers with 1:1 mapping, where reset lines can be indexed by number
+ * without gaps.
  */
 static int of_reset_simple_xlate(struct reset_controller_dev *rcdev,
 			  const struct of_phandle_args *reset_spec)

include/linux/reset-controller.h

@@ -62,7 +62,8 @@ struct reset_control_lookup {
  * @of_node: corresponding device tree node as phandle target
  * @of_reset_n_cells: number of cells in reset line specifiers
  * @of_xlate: translation function to translate from specifier as found in the
- *            device tree to id as given to the reset control ops
+ *            device tree to id as given to the reset control ops, defaults
+ *            to :c:func:`of_reset_simple_xlate`.
  * @nr_resets: number of reset controls in this reset controller device
  */
 struct reset_controller_dev {