CONFIG_SIBYTE_SB1xxx_SOC is not available for thedefaultarchitecture x86.
Result is shown for architecture mips
Support for Broadcom BCM1xxx SOCs (EXPERIMENTAL)
configname: CONFIG_SIBYTE_SB1xxx_SOC
Linux/MIPS Kernel Configuration
└─>Machine selection
└─>Support for Broadcom BCM1xxx SOCs (EXPERIMENTAL)