CONFIG_SOC_RT288X is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

RT288x

modulename: rt288x.ko

and/or

pci-rt2880.ko

configname: CONFIG_SOC_RT288X

Ralink SoC selection
└─>RT288x
In linux kernel since version 3.1 (release Date: 2011-10-24)  
source code:
/arch/mips/ralink/rt288x.c