1. Main issue.
The Kconfig doc for RTC_HCTOSYS_DEVICE says the RTC should be in UTC, but it can be in the local timezone, at least for most practical uses. So an explanation like this should be added: "In boots, the kernel interprets the date as UTC. If the device is in a local timezone, the timezone info should be set to the kernel before mounting any writable filesystems. Resuming is always correct independent of the timezone." (Sorry, I only know x86/amd64 personal desktops, and can show only the direction of fix.)
I'd like this fix since RTC_HCTOSYS=y is very useful, including resumes from s2ram and s2disk, and local TZ shouldn't be a reason to give it up. (Though it's irrelevant to the users of most distros.)
2. The doc location.
The doc line "Initialization is done when the system starts up, and when it resumes from a low power state." (and/or the fixed new sentence above) should be moved from RTC_HCTOSYS_DEVICE to RTC_HCTOSYS, since it's independent of the device, and has nothing to do with RTC_SYSTOHC, either.