regulator/of_get_regulator: add child path to find the regulator supplier

when the VIR_LDO1 regulator supplier is it's brother,
we can't find the supplier.

example code :
&vir_regulator {
	ldo0_vir: ldo0-virtual {
		regulator-compatible = "VIR_LDO0";
		regulator-name= "VIR_LDO0";
		regulator-min-microvolt = <1000000>;
		regulator-max-microvolt = <2000000>;
	};
	ldo1_vir: ldo1-virtual {
		regulator-compatible = "VIR_LDO1";
		regulator-name= "VIR_LDO1";
		regulator-min-microvolt = <1000000>;
		regulator-max-microvolt = <3000000>;
		ldo1-supply = <&ldo0_vir>;
	};
	...
}

so we add the child ptah to find the suppier.
Signed-off-by: zoro <long17.cool@163.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -227,6 +227,37 @@ static void regulator_unlock_supply(struct regulator_dev *rdev)
 	}
 }
 
+/**
+ * of_get_child_regulator - get a child regulator device node
+ * based on supply name
+ * @parent: Parent device node
+ * @prop_name: Combination regulator supply name and "-supply"
+ *
+ * Traverse all child nodes.
+ * Extract the child regulator device node corresponding to the supply name.
+ * returns the device node corresponding to the regulator if found, else
+ * returns NULL.
+ */
+static struct device_node *of_get_child_regulator(struct device_node *parent,
+						  const char *prop_name)
+{
+	struct device_node *regnode = NULL;
+	struct device_node *child = NULL;
+
+	for_each_child_of_node(parent, child) {
+		regnode = of_parse_phandle(child, prop_name, 0);
+
+		if (!regnode) {
+			regnode = of_get_child_regulator(child, prop_name);
+			if (regnode)
+				return regnode;
+		} else {
+			return regnode;
+		}
+	}
+	return NULL;
+}
+
 /**
  * of_get_regulator - get a regulator device node based on supply name
  * @dev: Device pointer for the consumer (of regulator) device
@@ -247,6 +278,10 @@ static struct device_node *of_get_regulator(struct device *dev, const char *supp
 	regnode = of_parse_phandle(dev->of_node, prop_name, 0);
 
 	if (!regnode) {
+		regnode = of_get_child_regulator(dev->of_node, prop_name);
+		if (regnode)
+			return regnode;
+
 		dev_dbg(dev, "Looking up %s property in node %pOF failed\n",
 				prop_name, dev->of_node);
 		return NULL;