tty: ar933x_uart: add device tree support and binding documentation

* Qualcomm Atheros AR9330 High-Speed UART

Required properties:

- compatible: Must be "qca,ar9330-uart"

- reg: Specifies the physical base address of the controller and

  the length of the memory mapped region.

- interrupt-parent: The phandle for the interrupt controller that

  services interrupts for this device.

- interrupts: Specifies the interrupt source of the parent interrupt

  controller. The format of the interrupt specifier depends on the

  parent interrupt controller.

Additional requirements:

  Each UART port must have an alias correctly numbered in "aliases"

  node.

Example:

	aliases {

		serial0 = &uart0;

	};

	uart0: uart@18020000 {

		compatible = "qca,ar9330-uart";

		reg = <0x18020000 0x14>;

		interrupt-parent = <&intc>;

		interrupts = <3>;

	};

#include <linux/sysrq.h>

#include <linux/delay.h>

#include <linux/platform_device.h>

#include <linux/of.h>

#include <linux/of_platform.h>

#include <linux/tty.h>

#include <linux/tty_flip.h>

#include <linux/serial_core.h>

	struct uart_port *port;

	struct resource *mem_res;

	struct resource *irq_res;

	struct device_node *np;

	unsigned int baud;

	int id;

	int ret;

	np = pdev->dev.of_node;

	if (config_enabled(CONFIG_OF) && np) {

		id = of_alias_get_id(np, "serial");

		if (id < 0) {

			dev_err(&pdev->dev, "unable to get alias id, err=%d\n",

				id);

			return id;

		}

	} else {

		id = pdev->id;

		if (id == -1)

			id = 0;

	}

	if (id > CONFIG_SERIAL_AR933X_NR_UARTS)

		return -EINVAL;

	return 0;

}

#ifdef CONFIG_OF

static const struct of_device_id ar933x_uart_of_ids[] = {

	{ .compatible = "qca,ar9330-uart" },

	{},

};

MODULE_DEVICE_TABLE(of, ar933x_uart_of_ids);

#endif

static struct platform_driver ar933x_uart_platform_driver = {

	.probe		= ar933x_uart_probe,

	.remove		= ar933x_uart_remove,

	.driver		= {

		.name		= DRIVER_NAME,

		.owner		= THIS_MODULE,

		.of_match_table = of_match_ptr(ar933x_uart_of_ids),

	},

};