diff --git a/doc/manual.md.in b/doc/manual.md.in
index a4a73a913097a..46821be05ed68 100644
--- a/doc/manual.md.in
+++ b/doc/manual.md.in
@@ -12,3 +12,8 @@ stdenv.md
 builders.md
 contributing.md
 ```
+
+```{=include=} appendix
+stdenv/platform-support-tiers.chapter.md
+```
+
diff --git a/doc/stdenv/platform-support-tiers.chapter.md b/doc/stdenv/platform-support-tiers.chapter.md
new file mode 100644
index 0000000000000..9a3fb84e430ba
--- /dev/null
+++ b/doc/stdenv/platform-support-tiers.chapter.md
@@ -0,0 +1,88 @@
+# Platform Support Tiers {#platform-support-tiers}
+
+In the context of Nixpkgs, a *platform* means an attrset which typechecks against `lib.systems.parsed.types.parsedPlatform`.  This includes a CPU architecture, bitwidth, and endianness and may also include: an OS kernel, environment (also called "C library"), choice of compiler and linker, option to link statically, and other data.
+
+Nixpkgs defines 7 platform *support tiers*, meaning levels of support for each platform.
+
+- **TODO**: change "build successfully" to a definition of "work" that includes tests?
+- **TODO**: mention binary cache?
+
+## Tier 1 {#platform-support-tier-1}
+
+These platforms receive the highest level of support, meaning that every
+platform-compatible package in Nixpkgs must successfully build in the Hydra and OfBorg CIs.
+**TODO**: this seems to not be entirely true for Hydra, but true for OfBorg.
+
+- `x86_64-linux-gnu` using `gcc`
+
+## Tier 2 {#platform-support-tier-2}
+
+Many of the packages are required to build successfully on these platforms in CI, the rest are supported on a best-effort basis by dedicated platform maintainers.
+**TODO**: link teams
+
+- `aarch64-linux`, `gcc+glibc`
+- `x86_64-darwin`, `clang+Darwin/macOS`
+
+## Tier 3 {#platform-support-tier-3}
+
+None of the packages for these platforms are required to build successfully in
+CI, but it is expected that most of them will build successfully.
+
+- `i686-linux-gnu`, `gcc`
+- `armv{6,7,8}*-linux-gnu`, `gcc`
+- `armv{6,7,8}*-linux-gnu`, `gcc`, cross-compilation
+- `aarch64-linux-gnu`, `gcc`, cross-compilation
+- `mipsel-linux-gnu`, `gcc`
+- `x86_64-linux-musl`, `gcc`
+
+## Tier 4 {#platform-support-tier-4}
+
+Some of the packages for these platforms are expected to work. The
+[`exotic-platform-maintainers`
+Team](https://github.com/orgs/NixOS/teams/exotic-platform-maintainers) is
+responsible for this platform.
+
+- `aarch64-none`
+- `avr`
+- `arm-none`
+- `i686-none`
+- `x86_64-none`
+- `powerpc-none`
+- `powerpcle-none`
+- `powerpc64le-linux-gnu`
+- `mips64el-linux-gnuabi64`
+- `x86_64-mingw32`
+- `i686-mingw32`
+- `x86_64-linux-musl`, `gcc` — static
+- `x86_64-linux-gnu`, `clang`
+- `x86_64-linux-gnu`, `clang` — `llvm` linker
+- `x86_64-linux-android`
+- `aarch64-linux-android`
+- `armv{7,8}-linux-android`
+
+## Tier 5 {#platform-support-tier-5}
+
+A small number of packages might build successfully on these platforms.
+
+- `x86_64-linux`, `gcc`+`glibc` — static
+- `x86_64-linux-gnu`, `gcc` `llvm` linker
+
+## Tier 6 {#platform-support-tier-6}
+
+These platforms are defined in Nixpkgs, but no packages are expected to build on them.
+
+- `wasm-wasi`
+
+## Tier 7 {#platform-support-tier-7}
+
+No current support, but previous support or clear path to add support.
+
+- `aarch64-darwin`
+- `i686-darwin`
+- `x86_64-freebsd`
+- `i686-solaris`
+- `x86_64-illumos`
+
+## Further reading {#platform-support-tiers-further-reading}
+
+For a formal definition of platform support tiers, see [RFC046](https://github.com/7c6f434c/rfcs/blob/platform-support-tiers/rfcs/0046-platform-support-tiers.md).