dt-bindings: bus: document ETZPC

Document ETZPC (Extended TrustZone protection controller). ETZPC is a
firewall controller.
Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Documentation/devicetree/bindings/bus/st,stm32-etzpc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/bus/st,stm32-etzpc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STM32 Extended TrustZone protection controller
+
+description: |
+  The ETZPC configures TrustZone security in a SoC having bus masters and
+  devices with programmable-security attributes (securable resources).
+
+maintainers:
+  - Gatien Chevallier <gatien.chevallier@foss.st.com>
+
+select:
+  properties:
+    compatible:
+      contains:
+        const: st,stm32-etzpc
+  required:
+    - compatible
+
+properties:
+  compatible:
+    items:
+      - const: st,stm32-etzpc
+      - const: simple-bus
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+  ranges: true
+
+  "#access-controller-cells":
+    const: 1
+    description:
+      Contains the firewall ID associated to the peripheral.
+
+patternProperties:
+  "^.*@[0-9a-f]+$":
+    description: Peripherals
+    type: object
+
+    additionalProperties: true
+
+    required:
+      - access-controllers
+
+required:
+  - compatible
+  - reg
+  - "#address-cells"
+  - "#size-cells"
+  - "#access-controller-cells"
+  - ranges
+
+additionalProperties: false
+
+examples:
+  - |
+    // In this example, the usart2 device refers to rifsc as its access
+    // controller.
+    // Access rights are verified before creating devices.
+
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    #include <dt-bindings/clock/stm32mp13-clks.h>
+    #include <dt-bindings/reset/stm32mp13-resets.h>
+
+    etzpc: bus@5c007000 {
+        compatible = "st,stm32-etzpc", "simple-bus";
+        reg = <0x5c007000 0x400>;
+        #address-cells = <1>;
+        #size-cells = <1>;
+        #access-controller-cells = <1>;
+        ranges;
+
+        usart2: serial@4c001000 {
+            compatible = "st,stm32h7-uart";
+            reg = <0x4c001000 0x400>;
+            interrupts-extended = <&exti 27 IRQ_TYPE_LEVEL_HIGH>;
+            clocks = <&rcc USART2_K>;
+            resets = <&rcc USART2_R>;
+            wakeup-source;
+            dmas = <&dmamux1 43 0x400 0x5>,
+                    <&dmamux1 44 0x400 0x1>;
+            dma-names = "rx", "tx";
+            access-controllers = <&etzpc 17>;
+        };
+    };