default or selected kernelversion does not have config value CONFIG_MTD_NAND_NUC900.
Result is shown for kernelversion 6.9.9

Support for NAND on Nuvoton NUC9xx/w90p910 evaluation boards.

modulename: nuc900_nand.ko

configname: CONFIG_MTD_NAND_NUC900

Linux Kernel Configuration
└─>Device Drivers
└─>Memory Technology Device (MTD) support
└─>Raw/Parallel NAND Device Support
└─>Support for NAND on Nuvoton NUC9xx/w90p910 evaluation boards.
In linux kernel since version 2.6.35 (release Date: 2010-08-01)  
This enables the driver for the NAND Flash on evaluation board based
on w90p910 / NUC9xx.

source code:
drivers/mtd/nand//raw/nuc900_nand.c