CONFIG_ARCH_S3C64XX is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

Samsung S3C64XX (deprecated, see help)

configname: CONFIG_ARCH_S3C64XX

Linux Kernel Configuration
└─>Samsung S3C64XX (deprecated, see help)
In linux kernel since version 2.6.29 (release Date: 2009-03-23)  
Samsung S3C64XX series based systems

The platform is deprecated and scheduled for removal. Please reach to
the maintainers of the platform and linux-samsung-soc@vger.kernel.org if
you still use it.
Without such feedback, the platform will be removed after 2024.