serial: 8250_uniphier: add auto-flow-control support

Add selective auto-flow-control support for UniPhier serial driver.
Signed-off-by: Dai Okamura <okamura.dai@socionext.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/uniphier-uart.txt

@@ -6,6 +6,9 @@ Required properties:
 - interrupts: a single interrupt specifier.
 - clocks: phandle to the input clock.
 
+Optional properties:
+-auto-flow-control: enable automatic flow control support.
+
 Example:
 	aliases {
 		serial0 = &serial0;

drivers/tty/serial/8250/8250_uniphier.c

@@ -222,6 +222,9 @@ static int uniphier_uart_probe(struct platform_device *pdev)
 	up.port.flags = UPF_FIXED_PORT | UPF_FIXED_TYPE;
 	up.capabilities = UART_CAP_FIFO;
 
+	if (of_property_read_bool(dev->of_node, "auto-flow-control"))
+		up.capabilities |= UART_CAP_AFE;
+
 	up.port.serial_in = uniphier_serial_in;
 	up.port.serial_out = uniphier_serial_out;
 	up.dl_read = uniphier_serial_dl_read;