diff --git a/Documentation/devicetree/bindings/mailbox/fsl,mu.yaml b/Documentation/devicetree/bindings/mailbox/fsl,mu.yaml
index 675ad9de15bb..a337bcd80c4a 100644
--- a/Documentation/devicetree/bindings/mailbox/fsl,mu.yaml
+++ b/Documentation/devicetree/bindings/mailbox/fsl,mu.yaml
@@ -28,6 +28,7 @@ properties:
       - const: fsl,imx7ulp-mu
       - const: fsl,imx8ulp-mu
       - const: fsl,imx8-mu-scu
+      - const: fsl,imx8ulp-mu-s4
       - items:
           - enum:
               - fsl,imx7s-mu