CONFIG_S3C_DEV_I2C3 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_S3C_DEV_I2C3 (not configurable)

modulename: dev-i2c3.ko

configname: CONFIG_S3C_DEV_I2C3

Linux Kernel Configuration
└─>S3C_DEV_I2C3
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
Compile in platform device definition for I2C controller 3

source code:
arch/arm/plat-samsung/dev-i2c3.c
depends
CONFIG_PLAT_SAMSUNG |
| CONFIG_SAMSUNG_ATAGS