CONFIG_TARGET_ISA_REV is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

CONFIG_TARGET_ISA_REV (not configurable)

configname: CONFIG_TARGET_ISA_REV

Linux Kernel Configuration
└─>TARGET_ISA_REV
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
Reflects the ISA revision being targeted by the kernel build. This
is effectively the Kconfig equivalent of MIPS_ISA_REV.