Detect UART port names on BananaPi M3

Question

I'm trying to detect the UART port names for a BananaPi M3 device running a Raspbian so I can do a simple test to send and receive some data on it. I connected the RX and TX pins of the UART connector with a simple jumper but I cannot detect the actual name of the ports. The pins are described here的下划线但我找不到他们的名字。
到目前为止我所做的测试没有成功：

ser = serial.Serial('/dev/ttyS1', 115200, timeout = 1)
    num = ser.write("test\n")
ser2 = serial.Serial('/dev/ttyS2', 115200, timeout = 1)
    data = ser2.read(100)

因此，如何检测到UART端口名称。
谢谢