regulator: pwm: Document pwm-dutycycle-unit and pwm-dutycycle-range

Document the pwm-dutycycle-unit and pwm-dutycycle-range properties.
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Brian Norris <briannorris@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/regulator/pwm-regulator.txt

@@ -34,6 +34,18 @@ Only required for Voltage Table Mode:
 			    First cell is voltage in microvolts (uV)
 			    Second cell is duty-cycle in percent (%)
 
+Optional properties for Continuous mode:
+- pwm-dutycycle-unit:	Integer value encoding the duty cycle unit. If not
+			defined, <100> is assumed, meaning that
+			pwm-dutycycle-range contains values expressed in
+			percent.
+
+- pwm-dutycycle-range:	Should contain 2 entries. The first entry is encoding
+			the dutycycle for regulator-min-microvolt and the
+			second one the dutycycle for regulator-max-microvolt.
+			Duty cycle values are expressed in pwm-dutycycle-unit.
+			If not defined, <0 100> is assumed.
+
 NB: To be clear, if voltage-table is provided, then the device will be used
 in Voltage Table Mode.  If no voltage-table is provided, then the device will
 be used in Continuous Voltage Mode.
@@ -53,6 +65,13 @@ Continuous Voltage With Enable GPIO Example:
 		regulator-min-microvolt = <1016000>;
 		regulator-max-microvolt = <1114000>;
 		regulator-name = "vdd_logic";
+		/* unit == per-mille */
+		pwm-dutycycle-unit = <1000>;
+		/*
+		 * Inverted PWM logic, and the duty cycle range is limited
+		 * to 30%-70%.
+		 */
+		pwm-dutycycle-range <700 300>; /* */
 	};
 
 Voltage Table Example: