CONFIG_CPU_P5600 is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

MIPS Warrior P5600

configname: CONFIG_CPU_P5600

CPU type
└─>MIPS Warrior P5600
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
Choose this option to build a kernel for MIPS Warrior P5600 CPU.
It's based on MIPS32r5 ISA with XPA, EVA, dual/quad issue exec pipes,
MMU with two-levels TLB, UCA, MSA, MDU core level features and system
level features like up to six P5600 calculation cores, CM2 with L2
cache, IOCU/IOMMU (though might be unused depending on the system-
specific IP core configuration), GIC, CPC, virtualisation module,
eJTAG and PDtrace.