CONFIG_SOC_SIFIVE is not available for thedefaultarchitecture x86.
Result is shown for architecture riscv
SiFive SoCs
configname: CONFIG_SOC_SIFIVE
Linux Kernel Configuration
└─>SoC selection
└─>SiFive SoCs
In linux kernel since version 4.14.326 (release Date: 2023-09-23)
This enables support for SiFive SoC platform hardware.