[RFC PATCH 3/4] dt-bindings: mtd: add OTP bindings

[Michael Walle <michael@walle.cc>]

Flash devices can have one-time-programmable regions. Add a nvmem
binding so they can be used as a nvmem provider.

Signed-off-by: Michael Walle <michael@walle.cc>
---
 .../devicetree/bindings/mtd/mtd.yaml          | 71 +++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/Documentation/devicetree/bindings/mtd/mtd.yaml b/Documentation/devicetree/bindings/mtd/mtd.yaml
index 321259aab0f6..2b852f91a6a9 100644
--- a/Documentation/devicetree/bindings/mtd/mtd.yaml
+++ b/Documentation/devicetree/bindings/mtd/mtd.yaml
@@ -21,6 +21,25 @@ properties:
       based name) in order to ease flash device identification and/or
       describe what they are used for.
 
+patternProperties:
+  "^otp(-[0-9]+)?":
+    type: object
+    $ref: ../nvmem/nvmem.yaml#
+
+    description: |
+      An OTP memory region. Some flashes provide a one-time-programmable
+      memory whose content can either be programmed by a user or is already
+      pre-programmed by the factory. Some flashes might provide both.
+
+    properties:
+      compatible:
+        enum:
+          - mtd-user-otp
+          - mtd-factory-otp
+
+    required:
+      - compatible
+
 additionalProperties: true
 
 examples:
@@ -36,4 +55,56 @@ examples:
         };
     };
 
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        flash@0 {
+            reg = <0>;
+            compatible = "some,flash";
+
+            otp {
+                compatible = "mtd-user-otp";
+                #address-cells = <1>;
+                #size-cells = <1>;
+
+                serial-number@0 {
+                    reg = <0 16>;
+                };
+            };
+        };
+    };
+
+  - |
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        flash@0 {
+            reg = <0>;
+            compatible = "some,flash";
+
+            otp-1 {
+                compatible = "mtd-factory-otp";
+                #address-cells = <1>;
+                #size-cells = <1>;
+
+                electronic-serial-number@0 {
+                    reg = <0 8>;
+                };
+            };
+
+            otp-2 {
+                compatible = "mtd-user-otp";
+                #address-cells = <1>;
+                #size-cells = <1>;
+
+                mac-address@0 {
+                    reg = <0 6>;
+                };
+            };
+        };
+    };
+
 ...
-- 
2.20.1