Serial port configuration with flow control

Serial port configuration with flow control

HW wiring is as follows:

The RTS (RequireToEnd, sending the request) is the output signal,used to indicate that the device is ready to receive data,Low level valid,indicates that the device can receive data。
CTS (CleartoSend, send allowed) is the input signal，used to determine whether to send data to the other side，low level valid，indicates that the device can send data to the other party。
Verify that the PIN is configured in FUART mode：

<PAD_FUART_RX        PINMUX_FOR_FUART_MODE_1       MDRV_PUSE_UTMI_RX>,
<PAD_FUART_TX        PINMUX_FOR_FUART_MODE_1       MDRV_PUSE_UTMI_TX>,
<PAD_FUART_CTS       PINMUX_FOR_FUART_MODE_1       MDRV_PUSE_FUART_CTS>,
<PAD_FUART_RTS       PINMUX_FOR_FUART_MODE_1       MDRV_PUSE_FUART_RTS>,

Verify that the FUART node has SCTP on：

        fuart: uart2@1F220400 {
            compatible = "sstar,uart";
            reg = <0x1F220400 0x100>, <0x1F220600 0x100>;
            interrupts = <GIC_SPI INT_IRQ_FUART IRQ_TYPE_LEVEL_HIGH>, <GIC_SPI INT_IRQ_URDMA IRQ_TYPE_LEVEL_HIGH>;
            sctp_enable = <1>;
            PAD = <PAD_FUART_CTX>
            clocks = <&CLK_fuart>;
            dma = <0>;
            tolerance = <2>
            status = "ok";
        };