CONFIG_ETRAX_SYNCHRONOUS_SERIAL1_DMA is not available for thedefaultarchitecture x86.
Result is shown for architecture cris
default or selected kernelversion does not have config value CONFIG_ETRAX_SYNCHRONOUS_SERIAL1_DMA.
Result is shown for kernelversion 6.7-rc3

Enable DMA on synchronous serial port 1.

configname: CONFIG_ETRAX_SYNCHRONOUS_SERIAL1_DMA

Linux Kernel Configuration
└─>Drivers for built-in interfaces
└─>Enable DMA on synchronous serial port 1.
In linux kernel since version 2.6.13 (release Date: 2005-08-28)  
A synchronous serial port can run in manual or DMA mode.
Selecting this option will make it run in DMA mode.