dt-bindings: clock: Add gpio-gate-clock-releasing

Document the gpio-gate-clock-releasing compatible string that enables
acquire/release GPIO semantics on gpio-gated clocks.

Signed-off-by: Richard Oliver <richard.oliver@raspberrypi.com>

Documentation/devicetree/bindings/clock/gpio-gate-clock.yaml

@@ -11,7 +11,15 @@ maintainers:
 
 properties:
   compatible:
-    const: gpio-gate-clock
+    enum:
+      - gpio-gate-clock
+      - gpio-gate-clock-releasing
+    description: |
+      Use "gpio-gate-clock" for normal operation where the GPIO is held for the
+      lifetime of the clock. Use "gpio-gate-clock-releasing" for power-sensitive
+      applications where the GPIO should be acquired only when the clock is
+      enabled and released when disabled, allowing shared regulators to be
+      powered down.
 
   clocks:
     maxItems: 1
@@ -40,3 +48,14 @@ examples:
         #clock-cells = <0>;
         enable-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
     };
+
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    /* Power-sensitive clock that releases GPIO when disabled */
+    clock {
+        compatible = "gpio-gate-clock-releasing";
+        clocks = <&parentclk>;
+        #clock-cells = <0>;
+        enable-gpios = <&gpio 1 GPIO_ACTIVE_HIGH>;
+    };