regulator: dt-bindings: mt6315: Add regulator supplies

The MT6315 family of PMICs has 4 buck regulators. Each regulator has a
separate supply.

Add these supplies to the device tree binding.

Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://patch.msgid.link/20260326081050.1115201-2-wenst@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: wens

Documentation/devicetree/bindings/regulator/mt6315-regulator.yaml

@@ -25,6 +25,15 @@ properties:
   reg:
     maxItems: 1
 
+  pvdd1-supply:
+    description: Supply for regulator vbuck1
+  pvdd2-supply:
+    description: Supply for regulator vbuck2
+  pvdd3-supply:
+    description: Supply for regulator vbuck3
+  pvdd4-supply:
+    description: Supply for regulator vbuck4
+
   regulators:
     type: object
     description: List of regulators and its properties
@@ -49,8 +58,11 @@ examples:
     pmic@6 {
       compatible = "mediatek,mt6315-regulator";
       reg = <0x6 0>;
+      pvdd1-supply = <&pp4200_z2>;
+      pvdd3-supply = <&pp4200_z2>;
 
       regulators {
+
         vbuck1 {
           regulator-min-microvolt = <300000>;
           regulator-max-microvolt = <1193750>;