CONFIG_TIMER_ACORN is not available for thedefaultarchitecture x86.
Result is shown for architecture arm
default or selected kernelversion does not have config value CONFIG_TIMER_ACORN.
Result is shown for kernelversion 6.2.5

CONFIG_TIMER_ACORN (not configurable)

modulename: time-acorn.ko

configname: CONFIG_TIMER_ACORN

Linux Kernel Configuration
└─>TIMER_ACORN
In linux kernel since version 2.6.12  
source code:
arch/arm/common/time-acorn.c
is depended by
CONFIG_ARCH_RPC