CONFIG_MACH_REALTEK_RTL is not available for thedefaultarchitecture x86.
Result is shown for architecture mips

Realtek RTL838x/RTL839x based machines

modulename: irq-realtek-rtl.ko

and/or

spi-realtek-rtl.ko

configname: CONFIG_MACH_REALTEK_RTL

System type
└─>Realtek RTL838x/RTL839x based machines
In linux kernel since version 4.14.326 (release Date: 2023-09-23)  
source code:
drivers/irqchip/irq-realtek-rtl.c

is selected by
CONFIG_GPIO_REALTEK_OTTO