It’s mostly just a rebase of our downstream patches on top of upstream 6.0 tree. The only meaningful difference when it comes to downstream changes (already present in 5.19, but 5.19 was never pushed out to be the default) is a change to lower SoC voltages a bit in order to reduce power consumption and produce less heat.
There are also two other minor changes since 5.18 (multicolor LED driver enabled in the config and alternative vendor-provided touchscreen driver included in the tree), but these have no effect on regular users at the moment.