There's a closed pull request on the void-packages repository

[WIP] New package: linux5.4.40-rt24
https://github.com/void-linux/void-packages/pull/22312

Description:

Just a modified version of the linux5.4 kernel template with the addition of the RT patch (https://kernel.org/pub/linux/kernel/projects/rt/5.4/). The kernel version and the void template are related to the version targeted by the patch (5.4.40 at present).

 - Changes in '*-dotconfig' files:

     - General setup -> Preemption Model:
        - from: Preemptible Kernel (Low-Latency Desktop)
        - to  : Fully Preemptible Kernel (Real-Time)

     - CPU Frequency scaling -> Default Governor:
        - from: ondemand
        - to  : performance

Only tested on x86_64.