CONFIG_SOC_MICROCHIP_POLARFIRE is not available for the selected architecture x86.
Result is shown for architecture riscv
Microchip PolarFire SoCs
configname: CONFIG_SOC_MICROCHIP_POLARFIRE
Linux Kernel Configuration
└─>SoC selection
└─>Microchip PolarFire SoCs
In linux kernel since version 5.2 (release Date: 2019-07-07)
This enables support for Microchip PolarFire SoC platforms.