docs: Add overview of development environment

Give an overview of the different tools required for development and
what they're used for.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

README.md

@@ -9,6 +9,7 @@ laptops.
 - [Flashing firmware](./doc/flashing.md)
 - [Debugging](./doc/debugging.md)
 - [Creating a custom keyboard layout](./doc/keyboard-layout-customization.md)
+- [Development environment](./doc/dev-env.md)
 - [Adding a new board](./doc/adding-a-new-board.md)
 
 ## Quickstart

doc/dev-env.md

@@ -0,0 +1,53 @@
+# Development environment
+
+## OS
+
+Linux is the only supported environment. Development is possible on a variety
+of distros. It is recommended to use the latest Pop!\_OS or Ubuntu release.
+
+The build server uses Ubuntu 20.04.
+
+## IDE/Editor
+
+Any editor that has support for [EditorConfig] may be used.
+
+No specific IDE or editor is required or recommended.
+
+## Toolset
+
+EC development depends on using distro-provided packages for the most of the
+toolset.
+
+A complete list of dependencies can be seen in `scripts/deps.sh`.
+
+### Cargo
+
+rustup manages the [Rust] toolchain, which includes cargo. Cargo is required
+for building the tools. It is the only part of the development toolset that is
+not installed through distro packages.
+
+### GNU Make
+
+[GNU Make] is used to automate the build process. It also provides targets for
+using ecflash (for flashing) and ectool (for console).
+
+### SDCC
+
+[SDCC] is the only practical open source toolset on Linux for targeting the
+8051 architecture (among others). It contains a collection of tools comparable
+to what you would expect from GCC for other development targets.
+
+SDCC contains language extensions to support the 8051 architecture. Refer to
+the [SDCC manual] for more information.
+
+Version 4.0.0 or newer should be used.
+
+**Note**: Fedora installs SDCC binaries to a non-standard location. Ensure that
+`PATH` includes `/usr/libexec/sdcc`.
+
+
+[EditorConfig]: https://editorconfig.org/
+[GNU Make]: https://www.gnu.org/software/make/
+[Rust]: https://www.rust-lang.org/
+[SDCC manual]: http://sdcc.sourceforge.net/doc/sdccman.pdf
+[SDCC]: http://sdcc.sourceforge.net/