CONFIG_ARCH_THEAD is not available for thedefaultarchitecture x86.
Result is shown for architecture riscv

T-HEAD RISC-V SoCs

configname: CONFIG_ARCH_THEAD

Linux Kernel Configuration
└─>SoC selection
└─>T-HEAD RISC-V SoCs
In linux kernel since version 6.5 (release Date: 2023-08-27)  
This enables support for the RISC-V based T-HEAD SoCs.