Porting newlib to new target using libgloss

[Hard Maker]

Hi list,
I'm trying to port newlib for use in a development kit. This use a 
Cortex M3, so I need to port only the specific system calls to work with 
the asociated  hardware.
There are some "guide" to do this? I'm googling from a week's and I can 
make the port using a custom CRT0, but I don't know how to reuse the 
startup code from libgloss for Cortex and add my code for the 
peripherical hardware.
Other question, when use newlib witch gcc, in C and C++ lenguage: ¿where 
can I read about the definitions needed in the linker script? I'm test 
with a linker script finded in internet but I know are some linkers 
script builded with the source, but I don't know how and which I need 
use (hosted or semihosted). Again, I'm using a cortex m3.

Thank's a lot.

Sergio