diff --git a/Documentation/devicetree/bindings/riscv/extensions.yaml b/Documentation/devicetree/bindings/riscv/extensions.yaml
index 577d7ae5576b..d4cde2a7b8b2 100644
--- a/Documentation/devicetree/bindings/riscv/extensions.yaml
+++ b/Documentation/devicetree/bindings/riscv/extensions.yaml
@@ -1211,6 +1211,38 @@ allOf:
           not:
             contains:
               const: zilsd
+  # All three Zicbo* extensions require their block size property as there's no
+  # default.
+  - if:
+      properties:
+        riscv,isa-extensions:
+          contains:
+            const: zicbom
+      required:
+        - riscv,isa-extensions
+    then:
+      required:
+        - riscv,cbom-block-size
+  - if:
+      properties:
+        riscv,isa-extensions:
+          contains:
+            const: zicbop
+      required:
+        - riscv,isa-extensions
+    then:
+      required:
+        - riscv,cbop-block-size
+  - if:
+      properties:
+        riscv,isa-extensions:
+          contains:
+            const: zicboz
+      required:
+        - riscv,isa-extensions
+    then:
+      required:
+        - riscv,cboz-block-size
 
 additionalProperties: true
 ...