dt-bindings: arm: firmware: Convert linaro,optee-tz to json schema

Convert linaro,optee-tz to json schema format for better documentation
and error checks.

NOTE: This change does introduce a stricter naming convention for
optee nodes.
Signed-off-by: Nishanth Menon <nm@ti.com>
Link: https://lore.kernel.org/r/20210426164008.20000-1-nm@ti.comSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.txt

-OP-TEE Device Tree Bindings
-
-OP-TEE is a piece of software using hardware features to provide a Trusted
-Execution Environment. The security can be provided with ARM TrustZone, but
-also by virtualization or a separate chip.
-
-We're using "linaro" as the first part of the compatible property for
-the reference implementation maintained by Linaro.
-
-* OP-TEE based on ARM TrustZone required properties:
-
-- compatible     : should contain "linaro,optee-tz"
-
-- method         : The method of calling the OP-TEE Trusted OS. Permitted
-                   values are:
-
-                   "smc" : SMC #0, with the register assignments specified
-		           in drivers/tee/optee/optee_smc.h
-
-                   "hvc" : HVC #0, with the register assignments specified
-		           in drivers/tee/optee/optee_smc.h
-
-
-
-Example:
-	firmware {
-		optee {
-			compatible = "linaro,optee-tz";
-			method = "smc";
-		};
-	};

Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/firmware/linaro,optee-tz.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: OP-TEE Device Tree Bindings
+
+maintainers:
+  - Jens Wiklander <jens.wiklander@linaro.org>
+
+description: |
+  OP-TEE is a piece of software using hardware features to provide a Trusted
+  Execution Environment. The security can be provided with ARM TrustZone, but
+  also by virtualization or a separate chip.
+
+  We're using "linaro" as the first part of the compatible property for
+  the reference implementation maintained by Linaro.
+
+properties:
+  $nodename:
+    const: optee
+
+  compatible:
+    const: linaro,optee-tz
+
+  method:
+    enum: [smc, hvc]
+    description: |
+      The method of calling the OP-TEE Trusted OS depending on smc or hvc
+      instruction usage.
+      SMC #0, register assignments
+      or
+      HVC #0, register assignments
+      register assignments are specified in drivers/tee/optee/optee_smc.h
+
+required:
+  - compatible
+  - method
+
+additionalProperties: false
+
+examples:
+  - |
+    firmware  {
+        optee  {
+            compatible = "linaro,optee-tz";
+            method = "smc";
+        };
+    };
+
+  - |
+    firmware  {
+        optee  {
+            compatible = "linaro,optee-tz";
+            method = "hvc";
+        };
+    };