default or selected kernelversion does not have config value CONFIG_IEEE80211_SOFTMAC.
Result is shown for kernelversion 5.19-rc1

Software MAC add-on to the IEEE 802.11 networking stack

modulename: ieee80211softmac.ko

configname: CONFIG_IEEE80211_SOFTMAC

Linux Kernel Configuration
└─>Networking
└─>Wireless
└─>Software MAC add-on to the IEEE 802.11 networking stack
In linux kernel since version 2.6.17 (release Date: 2006-06-17)  
This option enables the hardware independent software MAC addon
for the IEEE 802.11 networking stack.

source code: