very rarely people does and mostly academic people would prefer to learn but not to match to the pnoise results. General procedure is Find ISf from all devices and get the rms of that and use th lee formulas for the Overall Phase noise.
Following articles might help.
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7006708 (this is a innovative architecture but they have decribed how to evaluate PN noise from equation and they have correlated very well with sim as well as measurements)
http://gram.eng.uci.edu/faculty/green/public/courses/270c/materials/lectures/Wee... (from slide 52)
if you find better docs or procedure than the above please let me know kindly.
Are you aware of better procedure to find ISF??
Best Wishes,
Raj.