Pun aside, please have a look at gta04.sch page 15
you'll see:
DM3730CBP100-UART3, there
(H21)TX driving the RS232 TX pin via level shifter V1501, and a LED at V1502 TX. Here goes a second parallel LED for CIR and yes we will need an additional gate or FET, to switch that LED via GPIO175
(H20)RX which receives data from a) RS232 RX (via shifter), and b) from V1502 RX which is driven by a photo diode.

cursive annotations are for Neo900 CIR enhancement.


Now for the not so obvious but nevertheless even more nifty part in all that: In fremantle/N900 UART3 is the boot console (the pads under battery) ;-)
On a sidenote: this concept is ~5 years old and been introduced by me for *original* GTA04 that never got developed but only specified and then discontinued

HTH
/j