default or selected kernelversion does not have config value CONFIG_FWTTY_MAX_CARD_PORTS.
Result is shown for kernelversion 6.9.9

Maximum number of serial ports supported per adapter

configname: CONFIG_FWTTY_MAX_CARD_PORTS

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Maximum number of serial ports supported per adapter
In linux kernel since version 3.14 (release Date: 2014-03-30)  
Set this to the maximum number of serial ports each firewire
adapter supports. The actual number of serial ports registered
is set with the module parameter "ttys".