CONFIG_DEBUG_RK3X_UART3 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

RK3X UART3

configname: CONFIG_DEBUG_RK3X_UART3

Low-level debug console UART
└─>RK3X UART3
In linux kernel since version 3.11 (release Date: 2013-09-02)  

depends
 or CONFIG_ARCH_ROCKCHIP