Add {thumb,arm}v5te-none-eabi targets

src/doc/rustc/src/SUMMARY.md

@@ -19,6 +19,7 @@
     - [\*-apple-watchos\*](platform-support/apple-watchos.md)
     - [aarch64-nintendo-switch-freestanding](platform-support/aarch64-nintendo-switch-freestanding.md)
     - [armv4t-none-eabi](platform-support/armv4t-none-eabi.md)
+    - [armv5te-none-eabi](platform-support/armv5te-none-eabi.md)
     - [armv6k-nintendo-3ds](platform-support/armv6k-nintendo-3ds.md)
     - [armv7-unknown-linux-uclibceabi](platform-support/armv7-unknown-linux-uclibceabi.md)
     - [armv7-unknown-linux-uclibceabihf](platform-support/armv7-unknown-linux-uclibceabihf.md)

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

@@ -225,6 +225,7 @@ target | std | host | notes
 [`arm64_32-apple-watchos`](platform-support/apple-watchos.md) | ✓ | | ARM Apple WatchOS 64-bit with 32-bit pointers
 `armv4t-none-eabi` | * |  | ARMv4T A32
 `armv4t-unknown-linux-gnueabi` | ? |  |
+[`armv5te-none-eabi`](platform-support/armv5te-none-eabi.md) | * | | ARMv5TE A32
 `armv5te-unknown-linux-uclibceabi` | ? |  | ARMv5TE Linux with uClibc
 `armv6-unknown-freebsd` | ✓ | ✓ | ARMv6 FreeBSD
 `armv6-unknown-netbsd-eabihf` | ? |  |
@@ -291,6 +292,7 @@ target | std | host | notes
 `sparc64-unknown-netbsd` | ✓ | ✓ | NetBSD/sparc64
 [`sparc64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/sparc64
 `thumbv4t-none-eabi` | * |  | ARMv4T T32
+[`thumbv5te-none-eabi`](platform-support/armv5te-none-eabi.md) | * | | ARMv5TE T32
 `thumbv7a-pc-windows-msvc` | ? |  |
 `thumbv7a-uwp-windows-msvc` | ✓ |  |
 `thumbv7neon-unknown-linux-musleabihf` | ? |  | Thumb2-mode ARMv7a Linux with NEON, MUSL

src/doc/rustc/src/platform-support/armv5te-none-eabi.md

@@ -0,0 +1,75 @@
+# `armv5te-none-eabi`
+
+**Tier: 3**
+
+Bare-metal target for any cpu in the ARMv5TE architecture family, supporting
+ARM/Thumb code interworking (aka `a32`/`t32`), with ARM code as the default code
+generation.
+
+The `thumbv5te-none-eabi` target is the same as this one, but with THUMB code as the default.
+
+In particular this supports the main CPU of the Nintendo DS, but there's nothing DS
+specific with this target, so any ARMv5TE device should work fine.
+
+## Target Maintainers
+
+* [@QuinnPainter](https://github.com/QuinnPainter)
+
+## Requirements
+
+The target is cross-compiled, and uses static linking.
+
+By default, the `lld` linker included with Rust will be used.
+
+However, you may want to use the `arm-none-eabi-ld` linker instead. This can be obtained for Windows/Mac/Linux from the [ARM
+Developer Website][arm-dev], or possibly from your OS's package manager. To use it, add the following to your `.cargo/config.toml`:
+
+```toml
+[target.armv5te-none-eabi]
+linker = "arm-none-eabi-ld"
+```
+
+[arm-dev]: https://developer.arm.com/Tools%20and%20Software/GNU%20Toolchain
+
+This target doesn't provide a linker script, you'll need to bring your own
+according to the specific device you want to target. Pass
+`-Clink-arg=-Tyour_script.ld` as a rustc argument to make the linker use
+`your_script.ld` during linking.
+
+## Building Rust Programs
+
+Because it is Tier 3, rust does not yet ship pre-compiled artifacts for this target.
+
+Just use the `build-std` nightly cargo feature to build the `core` library. You
+can pass this as a command line argument to cargo, or your `.cargo/config.toml`
+file might include the following lines:
+
+```toml
+[unstable]
+build-std = ["core"]
+```
+
+Most of `core` should work as expected, with the following notes:
+* the target is "soft float", so `f32` and `f64` operations are emulated in
+  software.
+* integer division is also emulated in software.
+* the target is old enough that it doesn't have atomic instructions.
+
+`alloc` is also supported, as long as you provide your own global allocator.
+
+Rust programs are output as ELF files.
+
+For running on DS hardware, you'll need to use an external tool to bundle this ELF file into an NDS binary. The `ndstool` utility included with devkitARM is one such tool that can do this for you:
+
+```shell
+ndstool -c [out_nds] -9 [in_elf]
+```
+
+## Testing
+
+This is a cross-compiled target that you will need to emulate during testing.
+
+Because this is a device-agnostic target, and the exact emulator that you'll
+need depends on the specific device you want to run your code on.
+
+For example, when programming for the DS, you can use one of the several available DS emulators, such as [melonDS](https://melonds.kuribo64.net/).