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

QEMU Virt Machine

configname: CONFIG_SOC_VIRT

Linux Kernel Configuration
└─>SoC selection
└─>QEMU Virt Machine
In linux kernel since version 5.1 (release Date: 2019-05-05)  
This enables support for QEMU Virt Machine.