Just 2 cents which may help or may just tell you what you already know - a git grep in the core framework for tx_rf_port may be helpful. The following two lines are one example of a place mapping is done. Running OpenCPI w/ gbd and breaking on lines such as those below might help tracing things.
I grepped through the code and found in that RadioCtrlrNoOSTuneResamp.cc file where the initial PHY params were set to 1 instead of 0 (strange, but OK), but I don't see how just grepping for tx_rf_port got you to knowing where to look. For example, when I do "git grep tx_rf_port | wc -l" I get 39 results - 1 of which is the line that actually gives me a hint to look at getRfOutput().
Doing "git grep getRfOutput" gives me 4 lines in implementations with no comments on what the function actually does.
I'm all for suggestions and hints, but other than this mailing list, these new platform devices just seem like a lot of magic incantations and a ton of abstraction.
Brian