dt-bindings: serial: Convert sprd-uart to json-schema

* Spreadtrum serial UART

Required properties:

- compatible: must be one of:

  * "sprd,sc9836-uart"

  * "sprd,sc9860-uart", "sprd,sc9836-uart"

- reg: offset and length of the register set for the device

- interrupts: exactly one interrupt specifier

- clock-names: Should contain following entries:

  "enable" for UART module enable clock,

  "uart" for UART clock,

  "source" for UART source (parent) clock.

- clocks: Should contain a clock specifier for each entry in clock-names.

  UART clock and source clock are optional properties, but enable clock

  is required.

Optional properties:

- dma-names: Should contain "rx" for receive and "tx" for transmit channels.

- dmas: A list of dma specifiers, one for each entry in dma-names.

Example:

	uart0: serial@0 {

		compatible = "sprd,sc9860-uart",

			     "sprd,sc9836-uart";

		reg = <0x0 0x100>;

		interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;

		dma-names = "rx", "tx";

		dmas = <&ap_dma 19>, <&ap_dma 20>;

		clock-names = "enable", "uart", "source";

		clocks = <&clk_ap_apb_gates 9>, <&clk_uart0>, <&ext_26m>;

	};

# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)

# Copyright 2019 Unisoc Inc.

%YAML 1.2

---

$id: "http://devicetree.org/schemas/serial/sprd-uart.yaml#"

$schema: "http://devicetree.org/meta-schemas/core.yaml#"

title: Spreadtrum serial UART

maintainers:

  - Orson Zhai <orsonzhai@gmail.com>

  - Baolin Wang <baolin.wang7@gmail.com>

  - Chunyan Zhang <zhang.lyra@gmail.com>

properties:

  compatible:

    oneOf:

      - items:

          - enum:

              - sprd,sc9860-uart

          - const: sprd,sc9836-uart

      - const: sprd,sc9836-uart

  reg:

    maxItems: 1

  interrupts:

    maxItems: 1

  clocks:

    minItems: 1

    maxItems: 3

  clock-names:

    description: |

      "enable" for UART module enable clock, "uart" for UART clock, "source" 

      for UART source (parent) clock.

    items:

      - const: enable

      - const: uart

      - const: source

  dmas:

    minItems: 1

    maxItems: 2

  dma-names:

    minItems: 1

    items:

      - const: rx

      - const: tx

required:

  - compatible

  - reg

  - interrupts

examples:

  - |

    #include <dt-bindings/interrupt-controller/arm-gic.h>

    serial@0 {

      compatible = "sprd,sc9860-uart", "sprd,sc9836-uart";

      reg = <0x0 0x100>;

      interrupts = <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>;

      dma-names = "rx", "tx";

      dmas = <&ap_dma 19>, <&ap_dma 20>;

      clock-names = "enable", "uart", "source";

      clocks = <&clk_ap_apb_gates 9>, <&clk_uart0>, <&ext_26m>;

    };

...