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

CONFIG_ARCH_MICROCHIP_POLARFIRE (not configurable)

configname: CONFIG_ARCH_MICROCHIP_POLARFIRE

Linux Kernel Configuration
└─>SoC selection
└─>ARCH_MICROCHIP_POLARFIRE
In linux kernel since version 6.3 (release Date: 2023-04-23)  
is selected by
CONFIG_MCHP_CLK_MPFS