Regarding this issue, support for gdbserver has been implemented here:
https://github.com/fontamsoc/binutils-gdb/blob/b2eeeae0/gdbserver/linux-pu32-low.cc

Support for gdb has been implemented here:
https://github.com/fontamsoc/binutils-gdb/blob/b2eeeae0/gdb/pu32-tdep.c

gdb is able to successfully connect to gdbserver and start a program
on the target; however, gdb is unable to fetch registers and instead
shows <unavailable> as follow:

(gdb) info registers
r0             <unavailable>
r1             <unavailable>
r2             <unavailable>
r3             <unavailable>
r4             <unavailable>
r5             <unavailable>
r6             <unavailable>
r7             <unavailable>
r8             <unavailable>
r9             <unavailable>
r10            <unavailable>
r11            <unavailable>
r12            <unavailable>
r13            <unavailable>
r14            <unavailable>
r15            <unavailable>
pc             <unavailable>

Find attached full `gdbserver --debug --remote-debug` logs as well as gdb logs.

Any idea what might have been missed while implementing gdbserver support ?
Would you suggest ways to debug the issue ?