dt-bindings: Add devicetree bindings

Add snapshot of device tree bindings from keystone common kernel, branch
"android-mainline-keystone-qcom-release" at c4c12103f9c0 ("Snap for 9228065
from e32903b9a63bb558df8b803b076619c53c16baad to
android-mainline-keystone-qcom-release").

Change-Id: I7682079615cbd9f29340a5c1f2a1d84ec441a1f1
Signed-off-by: Melody Olvera <quic_molvera@quicinc.com>

bindings/regulator/vctrl.txt

@@ -0,0 +1,49 @@
+Bindings for Voltage controlled regulators
+==========================================
+
+Required properties:
+--------------------
+- compatible		  : must be "vctrl-regulator".
+- regulator-min-microvolt : smallest voltage consumers may set
+- regulator-max-microvolt : largest voltage consumers may set
+- ctrl-supply		  : The regulator supplying the control voltage.
+- ctrl-voltage-range	  : an array of two integer values describing the range
+			    (min/max) of the control voltage. The values specify
+			    the control voltage needed to generate the corresponding
+			    regulator-min/max-microvolt output voltage.
+
+Optional properties:
+--------------------
+- ovp-threshold-percent	: overvoltage protection (OVP) threshold of the
+			  regulator in percent. Some regulators have an OVP
+			  circuitry which shuts down the regulator when the
+			  actual output voltage deviates beyond a certain
+			  margin from the expected value for a given control
+			  voltage. On larger voltage decreases this can occur
+			  undesiredly since the output voltage does not adjust
+			  inmediately to changes in the control voltage. To
+			  avoid this situation the vctrl driver breaks down
+			  larger voltage decreases into multiple steps, where
+			  each step is within the OVP threshold.
+- min-slew-down-rate	: Describes how slowly the regulator voltage will decay
+			  down in the worst case (lightest expected load).
+			  Specified in uV / us (like main regulator ramp rate).
+			  This value is required when ovp-threshold-percent is
+			  specified.
+
+Example:
+
+	vctrl-reg {
+		compatible = "vctrl-regulator";
+		regulator-name = "vctrl_reg";
+
+		ctrl-supply = <&ctrl_reg>;
+
+		regulator-min-microvolt = <800000>;
+		regulator-max-microvolt = <1500000>;
+
+		ctrl-voltage-range = <200000 500000>;
+
+		min-slew-down-rate = <225>;
+		ovp-threshold-percent = <16>;
+	};