improve TODO.md

TODO.md

@@ -4,4 +4,35 @@ Improve the portability and reliability of this project's build process by:
 * creating a Dockerfile that stands up an ideal build machine for this project
 * adding a build command that builds the Rockbox file(s) using the aforementioned Dockerfile
 * neatly outputs all relevant build artifacts to a gitignored build directory
-* include a clean command (or update the existing one) to clean up the build dir
+* include a clean command (or update the existing one) to clean up the build dir
+
+## Clarified Requirements
+
+### Target Device
+- iPod Video 5.5th generation (30GB/60GB/80GB models)
+- Configure option: `22|ipodvideo`
+- Target macro: `IPOD_VIDEO`
+- Output file: `rockbox.ipod` (plus `rockbox.zip` containing the full installation package)
+
+### Toolchain
+- ARM cross-compiler: `arm-elf-eabi-gcc` version 9.5.0
+- Binutils version 2.38
+- Built via `tools/rockboxdev.sh` with option "A" (ARM)
+- The toolchain should be pre-installed in the Docker image for faster subsequent builds
+
+### Build System Dependencies
+Required packages for building the toolchain:
+- gcc, g++, make, patch, automake, libtool, autoconf, flex, bison
+- xz, bzip2, gzip (for archive extraction)
+- texinfo (provides makeinfo)
+- perl (required by configure script)
+- wget or curl (for downloading toolchain sources)
+- libgmp-dev, libmpfr-dev, libmpc-dev, libisl-dev (GCC build dependencies)
+
+### Build Artifacts
+Only output what's needed to install on the iPod:
+- `rockbox.zip` - The main installation package (unzip to iPod root)
+- `rockbox.ipod` - The firmware binary
+
+### Build Wrapper
+Use existing Makefile conventions in the repository. If modifying any Makefiles, update relevant documentation (CLAUDE.md, docs/README, etc.).