stm32_arch I don't know why, it is just another Cortex-M3 and in no way
special for lwIP. You seem to have some vendor polluted distribution.
sys_arch is the base of the port. Basically this one provides simple
definitions for mailboxes and semaphores for your OS, if you use one
(you do). You can use any other FreeRTOS port file.
Search the FreeRTOS web or the net, there are plenty of them
I think the maintainer lurks around this community also, search this
list, I think he already posted something on this some time ago.
You do need cc.h
The main ingredients there for Cortex-M3+ using CMSIS are:
#define LWIP_PLATFORM_BYTESWAP 1
#define LWIP_PLATFORM_HTONS(x) __REV16(x)
#define LWIP_PLATFORM_HTONL(x) __REV(x)
You have an example on my webpage for my port (bear in mind this one is
NO_SYS=1 so no mailboxes nor semaphores). Here:
http://scaprile.ldir.com.ar/cms/category/os/lwip-port