CONFIG_ARCH_STMP378X is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_ARCH_STMP378X.
Result is shown for kernelversion 5.4.69

Freescale STMP378x

modulename: stmp378x.ko

configname: CONFIG_ARCH_STMP378X

Select STMP3xxx chip family
└─>Freescale STMP378x
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
STMP378x refers to 3780 through 3789 chips

source code:
arch/arm/mach-stmp378x/stmp378x.c