serial: samsung: get fifosize via device tree

UART modules on some SoCs only differ in the fifosize of each
UART channel. Its useless to duplicate the drv_data structure
or create a compatible name for such a change.

We can get fifosize via the device tree nodes (not mandating it).

Also updates the documentation.

Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/samsung_uart.txt

@@ -29,6 +29,9 @@ Required properties:
 [1] Documentation/devicetree/bindings/interrupt-controller/interrupts.txt
 [2] Documentation/devicetree/bindings/clock/clock-bindings.txt
 
+Optional properties:
+- samsung,uart-fifosize: The fifo size supported by the UART channel
+
 Note: Each Samsung UART should have an alias correctly numbered in the
 "aliases" node, according to serialN format, where N is the port number
 (non-negative decimal integer) as specified by User's Manual of respective
@@ -51,4 +54,5 @@ Example:
 				"clk_uart_baud3";
 		clocks = <&clocks PCLK_UART1>, <&clocks PCLK_UART1>,
 				<&clocks SCLK_UART>;
+		samsung,uart-fifosize = <16>;
 	};

drivers/tty/serial/samsung.c

@@ -1295,9 +1295,15 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
 			dev_get_platdata(&pdev->dev) :
 			ourport->drv_data->def_cfg;
 
-	ourport->port.fifosize = (ourport->info->fifosize) ?
-		ourport->info->fifosize :
-		ourport->drv_data->fifosize[index];
+	if (pdev->dev.of_node)
+		of_property_read_u32(pdev->dev.of_node,
+			"samsung,uart-fifosize", &ourport->port.fifosize);
+
+	if (!ourport->port.fifosize) {
+		ourport->port.fifosize = (ourport->info->fifosize) ?
+			ourport->info->fifosize :
+			ourport->drv_data->fifosize[index];
+	}
 
 	probe_index++;