CONFIG_ETRAX_SERIAL_PORT4_TYPE_485FD is not available for thedefaultarchitecture x86.
Result is shown for architecture cris
default or selected kernelversion does not have config value CONFIG_ETRAX_SERIAL_PORT4_TYPE_485FD.
Result is shown for kernelversion 6.2.5

Ser4 is a full duplex RS-485 port


Ser4 default port type
└─>Ser4 is a full duplex RS-485 port
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
Configure serial port 4 to be a full duplex (four wires) RS-485 port.