CONFIG_ETRAX_SERIAL_PORT3_DMA3_IN is not available for thedefaultarchitecture x86.
Result is shown for architecture cris
default or selected kernelversion does not have config value CONFIG_ETRAX_SERIAL_PORT3_DMA3_IN.
Result is shown for kernelversion 6.2.5

Ser3 uses DMA3 for input


Ser3 DMA in channel
└─>Ser3 uses DMA3 for input
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
Enables the DMA3 input channel for ser3 (ttyS3).
If you do not enable DMA, an interrupt for each character will be
used when receiving data.
Normally you want to use DMA, unless you use the DMA channel for
something else.