CONFIG_ARCH_STMP3XXX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_STMP3XXX.
Result is shown for kernelversion 5.4.69

Freescale STMP3xxx


ARM system type
└─>Freescale STMP3xxx
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
Support for systems based on the Freescale 3xxx CPUs.