[PATCH v6 5/5] dt-bindings: phy: realtek: Add the doc about the Realtek SoC USB 3.0 PHY

[Stanley Chang <stanley_chang@realtek.com>]

Add the documentation explain the property about Realtek USB PHY driver.

Realtek DHC (digital home center) RTD SoCs support DWC3 XHCI USB
controller. Added the driver to drive the  USB 3.0 PHY transceivers.

Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
---
v5 to v6 change:
    Drop the labels of example.
v4 to v5 change:
    1. Remove the compatible realtek,usb3phy.
    2. Add the default of the property.
v3 to v4 change:
    1. Remove the parameter and non hardware properties from dts.
    2. Using the compatible data included the config and parameter
       in driver.
v2 to v3 change:
    1. Broken down into two patches, one for each of USB 2 & 3.
    2. Add more description about Realtek RTD SoCs architecture.
    3. Removed parameter v1 support for simplification.
    4. Revised the compatible name for fallback compatible.
    5. Remove some properties that can be set in the driver.
v1 to v2 change:
    Add phy-cells for generic phy driver
---
 .../bindings/phy/realtek,usb3phy.yaml         | 107 ++++++++++++++++++
 1 file changed, 107 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/phy/realtek,usb3phy.yaml

diff --git a/Documentation/devicetree/bindings/phy/realtek,usb3phy.yaml b/Documentation/devicetree/bindings/phy/realtek,usb3phy.yaml
new file mode 100644
index 000000000000..1a6cdc1ee073
--- /dev/null
+++ b/Documentation/devicetree/bindings/phy/realtek,usb3phy.yaml
@@ -0,0 +1,107 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2023 Realtek Semiconductor Corporation
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/realtek,usb3phy.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek DHC SoCs USB 3.0 PHY
+
+maintainers:
+  - Stanley Chang <stanley_chang@realtek.com>
+
+description:
+  Realtek USB 3.0 PHY support the digital home center (DHC) RTD series SoCs.
+  The USB 3.0 PHY driver is designed to support the XHCI controller. The SoCs
+  support multiple XHCI controllers. One PHY device node maps to one XHCI
+  controller.
+
+  RTD1295/RTD1619 SoCs USB
+  The USB architecture includes three XHCI controllers.
+  Each XHCI maps to one USB 2.0 PHY and map one USB 3.0 PHY on some
+  controllers.
+  XHCI controller#0 -- usb2phy -- phy#0
+                    |- usb3phy -- phy#0
+  XHCI controller#1 -- usb2phy -- phy#0
+  XHCI controller#2 -- usb2phy -- phy#0
+                    |- usb3phy -- phy#0
+
+  RTD1319/RTD1619b SoCs USB
+  The USB architecture includes three XHCI controllers.
+  Each XHCI maps to one USB 2.0 PHY and map one USB 3.0 PHY on controllers#2.
+  XHCI controller#0 -- usb2phy -- phy#0
+  XHCI controller#1 -- usb2phy -- phy#0
+  XHCI controller#2 -- usb2phy -- phy#0
+                    |- usb3phy -- phy#0
+
+  RTD1319d SoCs USB
+  The USB architecture includes three XHCI controllers.
+  Each xhci maps to one USB 2.0 PHY and map one USB 3.0 PHY on controllers#0.
+  XHCI controller#0 -- usb2phy -- phy#0
+                    |- usb3phy -- phy#0
+  XHCI controller#1 -- usb2phy -- phy#0
+  XHCI controller#2 -- usb2phy -- phy#0
+
+properties:
+  compatible:
+    enum:
+      - realtek,rtd1295-usb3phy
+      - realtek,rtd1319-usb3phy
+      - realtek,rtd1319d-usb3phy
+      - realtek,rtd1619-usb3phy
+      - realtek,rtd1619b-usb3phy
+
+  reg:
+    maxItems: 1
+
+  "#phy-cells":
+    const: 0
+
+  nvmem-cells:
+    maxItems: 1
+    description: A phandle to the tx lfps swing trim data provided by
+      a nvmem device, if unspecified, default values shall be used.
+
+  nvmem-cell-names:
+    items:
+      - const: usb_u3_tx_lfps_swing_trim
+
+  realtek,amplitude-control-coarse-tuning:
+    description:
+      This adjusts the signal amplitude for normal operation and beacon LFPS.
+      This value is a parameter for coarse tuning.
+      For different boards, if the default value is inappropriate, this
+      property can be assigned to adjust.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    default: 255
+    minimum: 0
+    maximum: 255
+
+  realtek,amplitude-control-fine-tuning:
+    description:
+      This adjusts the signal amplitude for normal operation and beacon LFPS.
+      This value is used for fine-tuning parameters.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    default: 65535
+    minimum: 0
+    maximum: 65535
+
+required:
+  - compatible
+  - reg
+  - "#phy-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    usb-phy@13e10 {
+        compatible = "realtek,rtd1319d-usb3phy";
+        reg = <0x13e10 0x4>;
+        #phy-cells = <0>;
+
+        nvmem-cells = <&otp_usb_u3_tx_lfps_swing_trim>;
+        nvmem-cell-names = "usb_u3_tx_lfps_swing_trim";
+
+        realtek,amplitude-control-coarse-tuning = <0x77>;
+    };
-- 
2.34.1