diff --git a/Documentation/devicetree/bindings/serial/st,stm32-usart.txt b/Documentation/devicetree/bindings/serial/st,stm32-usart.txt
index 9d3efed55deb243ff26e440f87496cfb23683c26..a6b19485c9dc09ba2c88091164e96ca33f2f59a7 100644
--- a/Documentation/devicetree/bindings/serial/st,stm32-usart.txt
+++ b/Documentation/devicetree/bindings/serial/st,stm32-usart.txt
@@ -13,6 +13,7 @@ Required properties:
 - clocks: The input clock of the USART instance
 
 Optional properties:
+- resets: Must contain the phandle to the reset controller.
 - pinctrl: The reference on the pins configuration
 - st,hw-flow-ctrl: bool flag to enable hardware flow control.
 - rs485-rts-delay, rs485-rx-during-tx, rs485-rts-active-low,