default or selected kernelversion does not have config value CONFIG_ISTALLION.
Result is shown for kernelversion 5.6.18

Stallion EC8/64, ONboard, Brumby support

modulename: istallion.ko

configname: CONFIG_ISTALLION

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Stallion EC8/64, ONboard, Brumby support
In linux kernel since version 2.6.20 (release Date: 2007-02-04)  
If you have an EasyConnection 8/64, ONboard, Brumby or Stallion
serial multiport card, say Y here. Make sure to read
Documentation/serial/stallion.txt.

To compile this driver as a module, choose M here: the
module will be called istallion.

source code: