The wiki article does not describe how to configure IR remote wakeup.
The IR wake code is hardcoded in the BL301 component of the boot firmware. ISTR that CE uses a custom version of BL301 source with some closed-source companion code to support external configuration. At some point I'll get around to investigating and then replicating something similar but a) done with open sources and mainline u-boot, b) upstreamed so everyone can benefit. I have a rather long to-do list at the moment though.
OK, so why does that "wakeup" file exist, if at all?
Because Google AI is crap and suggested modifying the device-tree to add wakeup-source; and thus the kernel now blindly exposes support for something that the hardware does not support being controlled from the kernel (it is hardcoded in BL301).