started with cadence raw netlist.
separated U1 and U2 to netlist-u1 and -u2
added PROCID pin which is tied to GND on U1, open on U2

identified special naming, identical for both processors:
                                  AC13     UNNAMED_1_RESPRT_I143_B : POR_override
                                  AD13     UNNAMED_1_BBRESPRT_I63_B :cclk_0
                                  AY22     UNNAMED_1_BBRESPRT_I115_B : LED7/9 : --> LED_A
                                  BB21     UNNAMED_1_BBRESPRT_I119_B : LED8/10 : --> LED_B
                                  BD21     UNNAMED_1_RESPRT_I31_B : VRP/DCI bank65
                                  H28      UNNAMED_8_RESPRT_I28_B : VRP bank71

-->u1.csv,u2.csv

further processing for U1 only, so far.
remove supply voltages,  Vref (MGT) with help of excel
--> u1-san1.csv

sanitize further:

cat u1-san1.csv |sed s.'4+4'.FF4. |sed s."U1_".. >u1-san2.csv

result looks rather sane and compatible to VHDL/XDC naming
comment out #:
JTAG, XADC,
T14	U1_INIT_B
AB14	U1_M0
Y14	U1_M1
V14	U1_M2
AK14	U1_PROGRAM_B
M14	U1_PUDC_B
AM14	U1_RDWR_FCS

to be done : add further comments in excel, swap columns and add columns for actual XDC syntax.
further: probably best to be done with tr/sed/awk etc: turn buses to XDC compatible index notation


some remarks:
MGT clocls are not indexed consecutively, but since they carry all the same signal, we can just as well renumber them as we wish. no need to relate to the PCB indexing at a later stage, I would think.

how would we like to name differential buses ? name_<n/p>_[index] ? Any other preference, eg. just a simple bus with even/odd assigned to p/n ? 

all bus renaming has been done in1-san3.csv, except MGT5_clk


 cat netlist-u2.txt |sed s._U2._U1. |sed s.U2_.U1_. |diff netlist-u1.txt - |less

tells us that both FPGAs have the same pin constraints with exception of the MGT_CLK indices which we wanted to sanitize anyway, since here the reference to the board level index doesn't make sense: the signals are all the same anyway.

final command for translating .csv to something sensible:
cat u1-san3.csv |tr [ $ |sed s.";$;".$. |tr $ [|tr ] $ |sed s.";$;".$. |tr $ ] |tr -s ";"|tr ";" " " >u1-san3.txt