diff --git a/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt b/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
index f8338d11fd2b610c7fe3b1a540d0c74886eb97ee..bd23302e84becbb255ab567be8da7a9489ad9184 100644
--- a/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
+++ b/Documentation/devicetree/bindings/pwm/pwm-stm32-lp.txt
@@ -7,6 +7,8 @@ See ../mfd/stm32-lptimer.txt for details about the parent node.
 
 Required parameters:
 - compatible:		Must be "st,stm32-pwm-lp".
+- #pwm-cells:		Should be set to 3. This PWM chip uses the default 3 cells
+			bindings defined in pwm.txt.
 
 Optional properties:
 - pinctrl-names: 	Set to "default".
@@ -18,6 +20,7 @@ Example:
 		...
 		pwm {
 			compatible = "st,stm32-pwm-lp";
+			#pwm-cells = <3>;
 			pinctrl-names = "default";
 			pinctrl-0 = <&lppwm1_pins>;
 		};