ggplot how to add labels on a second axis [duplicate]

Using the example data below and the respective plot, I simply want to add text for each of the three cyl groups at the top, e.g. for cyl = 4, I want to add a label like "abc", for cyl = 6 a label like "xyz" and so on.

I know that ggplot doesn't like secondary axes, and in my case I don't even want to display additional data, I just want to add second/alternative axis labels.

library(tidyverse)
mtcars |>
  mutate(cyl = as.character(cyl)) |>
  ggplot() +
  geom_tile(aes(x = cyl, y = gear, fill = disp))

This is what I have:

This is what I want:

Any ideas?