CONFIG_DTB_ECONET_SMARTFIBER_XP8421_B is not available for the selected architecture x86.
Result is shown for architecture mips
EN751221 SmartFiber XP8421-B
configname: CONFIG_DTB_ECONET_SMARTFIBER_XP8421_B
Devicetree selection
└─>EN751221 SmartFiber XP8421-B
In linux kernel since version 6.1.145 (release Date: 2025-07-14)
The SmartFiber XP8421-B is a device based on the EN751221 SoC.
It has 512MB of memory and 256MB of NAND flash. This kernel
needs only an appended initramfs to boot. It can be loaded
through XMODEM and booted from memory in the bootloader, or
it can be packed in tclinux.trx format and written to flash.
It has 512MB of memory and 256MB of NAND flash. This kernel
needs only an appended initramfs to boot. It can be loaded
through XMODEM and booted from memory in the bootloader, or
it can be packed in tclinux.trx format and written to flash.