default or selected kernelversion does not have config value CONFIG_NET_VENDOR_SUNPLUS.
Result is shown for kernelversion 6.9-rc5

Sunplus devices

configname: CONFIG_NET_VENDOR_SUNPLUS

Linux Kernel Configuration
└─>Device Drivers
└─>Network device support
└─>Ethernet driver support
└─>Sunplus devices
In linux kernel since version 5.2 (release Date: 2019-07-07)  
If you have a network (Ethernet) card belonging to this
class, say Y here.

Note that the answer to this question doesn't directly
affect the kernel: saying N will just cause the configurator
to skip all the questions about Sunplus cards. If you say Y,
you will be asked for your specific card in the following
questions.

depends
CONFIG_ETHERNET
CONFIG_NETDEVICES
CONFIG_ARCH_SUNPLUS or CONFIG_COMPILE_TEST

is selected by
CONFIG_SP7021_EMAC