@@ -0,0 +1,154 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/pse-pd/realtek,pse-mcu.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek/Broadcom PSE MCU
+
+maintainers:
+  - Jonas Jelonek <jelonek.jonas@gmail.com>
+
+description: |
+  Microcontroller (MCU) that fronts the PSE hardware on switches using
+  Realtek (RTL8238B, RTL8239, RTL8239C) or Broadcom (BCM59111, BCM59121)
+  PSE chips. The MCU exposes a small message-based protocol over either
+  I2C/SMBus or UART; the actual PSE silicon is not accessed directly. The
+  Realtek and Broadcom variants share this device tree contract but use
+  different protocol opcodes, selected by the compatible.
+
+  The compatible identifies the PSE-MCU protocol dialect, not a specific
+  part. The device here is the MCU: it presents a stable message protocol
+  documented by Realtek, with the PSE silicon behind it - Broadcom on
+  older boards, Realtek on newer - detected at runtime and not described
+  here. The MCU's own silicon is general-purpose and varies across
+  boards, so the 'realtek' vendor prefix names the protocol front-end
+  (following the google,cros-ec pattern); the '-rtk'/'-bcm' suffix
+  selects the Realtek or Broadcom dialect.
+
+  A single compatible per dialect covers both the I2C/SMBus and UART
+  attachments: the wire protocol is identical across them and the
+  transport is already expressed by the node's parent bus, so it is not
+  encoded in the compatible. Transport-specific properties differ
+  accordingly - the I2C attachment carries 'reg' (and, for Realtek,
+  'realtek,i2c-protocol'), while the UART attachment carries the serial
+  peripheral properties such as 'current-speed'.
+
+properties:
+  compatible:
+    enum:
+      - realtek,pse-mcu-rtk
+      - realtek,pse-mcu-brcm
+
+  reg:
+    maxItems: 1
+
+  power-supply:
+    description: Regulator supplying the PoE power rail.
+
+  enable-gpios:
+    maxItems: 1
+
+  realtek,i2c-protocol:
+    $ref: /schemas/types.yaml#/definitions/string
+    enum: [ i2c, smbus ]
+    description: |
+      Wire framing the MCU firmware expects on the I2C bus. "smbus" means
+      reads carry a leading command byte (0x00) and a repeated start; "i2c"
+      means bare 12-byte writes and reads with no command prefix. Only
+      applies to the Realtek I2C attachment.
+
+required:
+  - compatible
+
+allOf:
+  - $ref: pse-controller.yaml#
+  - $ref: /schemas/serial/serial-peripheral-props.yaml#
+  # The I2C attachment (identified by 'reg') cannot carry serial bus props.
+  - if:
+      required: [reg]
+    then:
+      properties:
+        current-speed: false
+        max-speed: false
+  # 'realtek,i2c-protocol' is meaningful only for the Realtek I2C attachment;
+  # the Broadcom variant and any UART attachment must not carry it.
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: realtek,pse-mcu-rtk
+      required: [reg]
+    then:
+      required:
+        - realtek,i2c-protocol
+    else:
+      properties:
+        "realtek,i2c-protocol": false
+
+unevaluatedProperties: false
+
+examples:
+  # Realtek PSE chip, I2C attachment (SMBus framing).
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethernet-pse@20 {
+            compatible = "realtek,pse-mcu-rtk";
+            reg = <0x20>;
+            realtek,i2c-protocol = "smbus";
+
+            pse-pis {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                pse-pi@0 {
+                    reg = <0>;
+                    #pse-cells = <0>;
+                };
+            };
+        };
+    };
+
+  # Broadcom PSE chip, I2C attachment.
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        ethernet-pse@20 {
+            compatible = "realtek,pse-mcu-brcm";
+            reg = <0x20>;
+
+            pse-pis {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                pse-pi@0 {
+                    reg = <0>;
+                    #pse-cells = <0>;
+                };
+            };
+        };
+    };
+
+  # Realtek PSE chip, UART attachment.
+  - |
+    serial {
+        ethernet-pse {
+            compatible = "realtek,pse-mcu-rtk";
+            current-speed = <115200>;
+
+            pse-pis {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                pse-pi@0 {
+                    reg = <0>;
+                    #pse-cells = <0>;
+                };
+            };
+        };
+    };