default or selected kernelversion does not have config value CONFIG_PINCTRL_UNIPHIER_PROXSTREAM2.
Result is shown for kernelversion 5.4.229

UniPhier ProXstream2 SoC pinctrl driver

modulename: pinctrl-proxstream2.ko

configname: CONFIG_PINCTRL_UNIPHIER_PROXSTREAM2

Linux Kernel Configuration
└─>Device Drivers
└─>Pin controllers
└─>UniPhier SoC pinctrl drivers
└─>UniPhier ProXstream2 SoC pinctrl driver
In linux kernel since version 4.3 (release Date: 2015-11-01)  
source code:
drivers/pinctrl/uniphier/pinctrl-proxstream2.c