dt-bindings: regulator: add stub regulator bindings

Add stub-regulator device bindings.  These devices can be used to
simulate any particular voltage regulator.

Change-Id: I5d15f825944747b6a0c95508219967bdd9590610
Signed-off-by: Xubin Bai <quic_xubibai@quicinc.com>

bindings/regulator/qcom,stub-regulator.yaml

@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/regulator/qcom,stub-regulator.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Qualcomm Technologies, Inc. Stub Regulators
+
+maintainers:
+  - David Collins <quic_collinsd@quicinc.com>
+
+description: |
+    stub-regulators are place-holder regulator devices which do not impact any
+    hardware state.  They provide a means for consumer devices to utilize all
+    regulator features for testing purposes.
+
+allOf:
+  - $ref: "regulator.yaml#"
+
+properties:
+  compatible:
+    const: qcom,stub-regulator
+
+  parent-supply:
+    description: phandle to the parent regulator node if one exists.
+
+  qcom,hpm-min-load:
+    description: |
+      Load current in uA which corresponds to the minimum load
+      which requires the regulator to be in high power mode.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+  qcom,system-load:
+    description: |
+      Load in uA present on regulator that is not captured by any
+      consumer request.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+required:
+  - compatible
+  - regulator-name
+
+additionalProperties: false
+
+examples:
+  - |
+    pm8026_l1: regulator-l1 {
+      compatible = "qcom,stub-regulator";
+      regulator-name = "8026_l1";
+      parent-supply = <&pm8026_s3>;
+      qcom,hpm-min-load = <10000>;
+      regulator-min-microvolt = <1225000>;
+      regulator-max-microvolt = <1225000>;
+    };
+...