Hi,
TRST is a well defined JTAG boundary scan signal, the only useful connection is to a JTAG programming adapter that supports it. USB Blaster doesn't use TRST, but if you are providing an interface for a full featured ARM debugger with trace functionality, you would connect it to the respective debug connector.
Official signal name according to JTAG IEEE Std. 1149 is TRST* to indicate active low operation. Because asterix is no legal symbol in many EDA systems, it's often omitted. nTRST would be a possible alternative, but it can cause confusion. I'd stay with TRST, keeping in mind that it's inverted. PCG document is clear about inverted function, in so far there's nothing to clarify, I believe.
Regards
Frank