default or selected kernelversion does not have config value CONFIG_PINMUX_U300.
Result is shown for kernelversion 5.16-rc3

U300 pinmux driver

modulename: pinmux-u300.ko

configname: CONFIG_PINMUX_U300

Linux Kernel Configuration
└─>Device Drivers
└─>Pin controllers
└─>U300 pinmux driver
In linux kernel since version 3.3 (release Date: 2012-03-18)  
source code:
drivers/pinctrl/pinmux-u300.c
selects
CONFIG_PINMUX


is depended by
CONFIG_MACH_U300