Rollup merge of #111389 - esp-rs:esp-idf-platform-support, r=jyn514

Add esp-idf platform-support page

As mentioned in #111369 (comment), the initial PR for esp-idf didn't include a platform support document which is required for the merge of  #111369.

Author: matthiaskrgr

src/doc/rustc/src/SUMMARY.md

@@ -27,6 +27,7 @@
     - [armv7-unknown-linux-uclibceabihf](platform-support/armv7-unknown-linux-uclibceabihf.md)
     - [\*-android and \*-androideabi](platform-support/android.md)
     - [\*-linux-ohos](platform-support/openharmony.md)
+    - [\*-esp-espidf](platform-support/esp-idf.md)
     - [\*-unknown-fuchsia](platform-support/fuchsia.md)
     - [\*-kmc-solid_\*](platform-support/kmc-solid.md)
     - [loongarch\*-unknown-linux-\*](platform-support/loongarch-linux.md)

src/doc/rustc/src/platform-support.md

@@ -297,7 +297,7 @@ target | std | host | notes
 `riscv32gc-unknown-linux-musl` |   |   | RISC-V Linux (kernel 5.4, musl + RISCV32 support patches)
 `riscv32im-unknown-none-elf` | * |  | Bare RISC-V (RV32IM ISA)
 [`riscv32imac-unknown-xous-elf`](platform-support/riscv32imac-unknown-xous-elf.md) | ? |  | RISC-V Xous (RV32IMAC ISA)
-`riscv32imc-esp-espidf` | ✓ |  | RISC-V ESP-IDF
+[`riscv32imc-esp-espidf`](platform-support/esp-idf.md) | ✓ |  | RISC-V ESP-IDF
 `riscv64gc-unknown-freebsd` |   |   | RISC-V FreeBSD
 `riscv64gc-unknown-fuchsia` |   |   | RISC-V Fuchsia
 `riscv64gc-unknown-linux-musl` |   |   | RISC-V Linux (kernel 4.20, musl 1.2.0)

src/doc/rustc/src/platform-support/esp-idf.md

@@ -0,0 +1,41 @@
+# `*-esp-espidf`
+
+**Tier: 3**
+
+Targets for the [ESP-IDF](https://github.com/espressif/esp-idf) development framework running on RISC-V and Xtensa CPUs.
+
+## Target maintainers
+
+- Ivan Markov [@ivmarkov](https://github.com/ivmarkov)
+- Scott Mabin [@MabezDev](https://github.com/MabezDev)
+
+## Requirements
+
+The target names follow this format: `$ARCH-esp-espidf`, where `$ARCH` specifies the target processor architecture. The following targets are currently defined:
+
+|          Target name           | Target CPU(s)         |
+|--------------------------------|-----------------------|
+| `riscv32imc-esp-espidf`        |  [ESP32-C3](https://www.espressif.com/en/products/socs/esp32-c3)             |
+
+The minimum supported ESP-IDF version is `v4.3`, though it is recommended to use the latest stable release if possible.
+
+## Building the target
+
+The target can be built by enabling it for a `rustc` build. The `build-std` feature is required to build the standard library for ESP-IDF. `ldproxy` is also required for linking, it can be installed from crates.io.
+
+```toml
+[build]
+target = ["$ARCH-esp-espidf"]
+
+[target.$ARCH-esp-espidf]
+linker = "ldproxy"
+
+[unstable]
+build-std = ["std", "panic_abort"]
+```
+
+The `esp-idf-sys` crate will handle the compilation of ESP-IDF, including downloading the relevant toolchains for the build.
+
+## Cross-compilation toolchains and C code
+
+`esp-idf-sys` exposes the toolchain used in the compilation of ESP-IDF, see the crate [documentation for build output propagation](https://github.com/esp-rs/esp-idf-sys#conditional-compilation) for more information.