Even though I just seem to be talking to myself, I thought I'd try to bring my contribution closer to completion. I eventually discovered that there seems to be an address conflict with the CIR on my PN62S. By changing the _ADR from Zero to 0x01 and recompiling my DSDT as above, ite-cir will happily see, and connect with the ITE8708. I have submitted a tech support request to Asus detailing my issue, hoping this, or an equivalent correction, will make its way into a future BIOS update. I also mentioned the PN50 length issue, so hopefully they will examine that as well. If I get any relevant response, I may provide an update. In the meantime, I'm using the script for grub from Updated `01_acpi` script. · GitHub to automatically load my custom DSDT.
Thanks for your input.
Unfortunately I haven't had the time to look further into my PN50. It's been sitting off for a few months now and I don't think I'll be able to test anything until the end of summer.
1. Regarding the linux-media link you have posted, it's the one that led me to a temporary solution for the PN50. I revived that discussion in that mailing list & posted a first version for a patch. I didn't have the time to follow it up, but I think one of the maintainers there did and added a final version of the patch patch to the kernel modules.
2. I also shortly fell into the 'rabbit hole' of trying to edit/recompile my BIOS DSDT tables for the PN50 when researching this. I didn't spend a lot of time though, as I couldn't recompile without errors/warnings and didn't know enough to overcome these.