CONFIG_S3C_DEV_WDT is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S3C_DEV_WDT (not configurable)

modulename: dev-wdt.ko

configname: CONFIG_S3C_DEV_WDT

Linux Kernel Configuration
└─>S3C_DEV_WDT
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
Complie in platform device definition for Watchdog Timer

source code:
arch/arm/plat-samsung/dev-wdt.c
depends
CONFIG_PLAT_SAMSUNG |
| CONFIG_SAMSUNG_ATAGS

is depended by
CONFIG_MACH_SMDK6410