How do I get started with uCLinux?
First try to build uClinux from source to get a feel for it (toolchain, memory consumption etc.). Then look at the tips for porting uClinux. The quick rundown:


Architecture: Check whether your architecture is supported or not. Create a new branch in linux/arch/ if needed. That step involves creating/modifying 20-30 files to handle CPU-specific instructions.
Platform: Your processor is already supported by an 
existing linux/arch branch, but has differences that impact the kernel and peripherals. Create a new branch in linux/arch//platform/. This step creates traps, vector inits and interrupt handlers and involves 6 files.
Board: Your architecture is very close to exiting platforms and only minor changes have to be made to the kernel (e.g. memory description/layout, external peripeherals).  


Usually you have to adjust the Makefiles and then fix all the complaints until it builds.