CONFIG_ETRAX_SYNCHRONOUS_SERIAL_PORT0 is not available for thedefaultarchitecture x86.
Result is shown for architecture cris

Synchronous serial port 0 enabled

configname: CONFIG_ETRAX_SYNCHRONOUS_SERIAL_PORT0

Linux Kernel Configuration
└─>Drivers for built-in interfaces
└─>Synchronous serial port 0 enabled
In linux kernel since version 2.6.13 (release Date: 2005-08-28)  
Enabled synchronous serial port 0.