CONFIG_S3C2412_PM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S3C2412_PM (not configurable)

modulename: s3c2412-pm.ko

configname: CONFIG_S3C2412_PM

Linux Kernel Configuration
└─>S3C2412_PM
In linux kernel since version 2.6.19 (release Date: 2006-11-29)  
Internal config node to apply S3C2412 power management

source code:
arch/arm/mach-s3c2410/s3c2412-pm.c
depends
CONFIG_ARCH_S3C2410

is depended by
CONFIG_CPU_S3C2412