[PATCH v4 1/2] dt-bindings: serial: Document WK2xxx SPI UART

[zjzhao@edatec.cn]

From: Zi Jie Zhao <zjzhao@edatec.cn>

Add a DT binding for the WK2xxx SPI to UART bridge ICs (WK2124, WK2132,
WK2168, WK2202 and WK2204) from Chengdu Weikai Microelectronics (WKmic).
Describe each UART channel with a serial@N child node carrying its serial
and RS-485 properties. Register the wkmic vendor prefix based on the vendor
website http://www.wkmic.com/.

Differentiate compatible strings by channel count and
register availability. Account for missing hardware flow-control and
RS-485 registers on WK2132 and WK2202. Reject serial@2 and serial@3 on the
two-channel members.

Require the standard clocks property for the single external reference
clock used by the chips.

Signed-off-by: Zi Jie Zhao <zjzhao@edatec.cn>
---
 .../bindings/serial/wkmic,wk2124.yaml         | 119 ++++++++++++++++++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 2 files changed, 121 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml

diff --git a/Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml b/Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml
new file mode 100644
index 000000000000..0f6ba8755e1c
--- /dev/null
+++ b/Documentation/devicetree/bindings/serial/wkmic,wk2124.yaml
@@ -0,0 +1,119 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/wkmic,wk2124.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: WKmic WK2xxx SPI to UART bridge
+
+maintainers:
+  - Zi Jie Zhao <zjzhao@edatec.cn>
+
+description:
+  The WK2xxx family (WK2124, WK2132, WK2168, WK2202 and WK2204) are SPI to
+  UART bridge ICs from WKmic (Chengdu Weikai Microelectronics). Each IC
+  exposes two or four full-duplex UART channels with 256-byte RX/TX FIFOs
+  through a single SPI slave interface and one interrupt line, and is
+  clocked from a single external reference clock. Each channel is
+  described by a "serial@N" child node that carries its own serial and
+  RS-485 properties.
+
+properties:
+  compatible:
+    enum:
+      - wkmic,wk2124
+      - wkmic,wk2132
+      - wkmic,wk2168
+      - wkmic,wk2202
+      - wkmic,wk2204
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    description:
+      When missing, the device driver uses polling instead.
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+patternProperties:
+  "^serial@[0-3]$":
+    type: object
+    description: A single UART channel of the chip.
+    allOf:
+      - $ref: /schemas/serial/serial.yaml#
+      - $ref: /schemas/serial/rs485.yaml#
+    properties:
+      reg:
+        description: UART channel number on the chip.
+        maximum: 3
+    required:
+      - reg
+    unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+  - clocks
+  - "#address-cells"
+  - "#size-cells"
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - wkmic,wk2132
+              - wkmic,wk2202
+    then:
+      patternProperties:
+        "^serial@[23]$": false
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    xtal: clock-11059200 {
+        compatible = "fixed-clock";
+        clock-frequency = <11059200>;
+        #clock-cells = <0>;
+    };
+
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        serial@0 {
+            compatible = "wkmic,wk2132";
+            reg = <0>;
+            spi-max-frequency = <10000000>;
+            clocks = <&xtal>;
+            interrupt-parent = <&gpio>;
+            interrupts = <24 IRQ_TYPE_LEVEL_LOW>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            serial@0 {
+                reg = <0>;
+            };
+
+            serial@1 {
+                reg = <1>;
+                rs485-rts-active-low;
+                linux,rs485-enabled-at-boot-time;
+            };
+        };
+    };
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml b/Documentation/devicetree/bindings/vendor-prefixes.yaml
index ba2002969373..cdc04229d642 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.yaml
+++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml
@@ -1907,6 +1907,8 @@ patternProperties:
     description: Wireless Tag (qiming yunduan)
   "^wits,.*":
     description: Shenzhen Merrii Technology Co., Ltd. (WITS)
+  "^wkmic,.*":
+    description: Chengdu Weikai Microelectronics Co., Ltd. (http://www.wkmic.com/)
   "^wlf,.*":
     description: Wolfson Microelectronics
   "^wm,.*":
-- 
2.43.0