Add platform markdown description

Author: agg23

src/doc/rustc/src/SUMMARY.md

@@ -20,6 +20,7 @@
     - [aarch64-apple-ios-sim](platform-support/aarch64-apple-ios-sim.md)
     - [\*-apple-tvos](platform-support/apple-tvos.md)
     - [\*-apple-watchos\*](platform-support/apple-watchos.md)
+    - [aarch64-apple-xros\*](platform-support/apple-xros.md)
     - [aarch64-nintendo-switch-freestanding](platform-support/aarch64-nintendo-switch-freestanding.md)
     - [armeb-unknown-linux-gnueabi](platform-support/armeb-unknown-linux-gnueabi.md)
     - [arm-none-eabi](platform-support/arm-none-eabi.md)

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

@@ -241,6 +241,8 @@ target | std | host | notes
 [`aarch64-apple-tvos-sim`](platform-support/apple-tvos.md) | ? |  | ARM64 tvOS Simulator
 [`aarch64-apple-watchos`](platform-support/apple-watchos.md) | ✓ |  | ARM64 Apple WatchOS
 [`aarch64-apple-watchos-sim`](platform-support/apple-watchos.md) | ✓ |  | ARM64 Apple WatchOS Simulator
+[`aarch64-apple-xros`](platform-support/apple-xros.md) | ✓ |  | ARM64 Apple visionOS
+[`aarch64-apple-xros-sim`](platform-support/apple-xros.md) | ✓ |  | ARM64 Apple visionOS Simulator
 [`aarch64-kmc-solid_asp3`](platform-support/kmc-solid.md) | ✓ |  | ARM64 SOLID with TOPPERS/ASP3
 [`aarch64-nintendo-switch-freestanding`](platform-support/aarch64-nintendo-switch-freestanding.md) | * |  | ARM64 Nintendo Switch, Horizon
 [`aarch64-pc-windows-gnullvm`](platform-support/pc-windows-gnullvm.md) | ✓ | ✓ |

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

@@ -0,0 +1,52 @@
+# aarch64-apple-xros\*
+
+-   aarch64-apple-xros
+-   aarch64-apple-xros-sim
+
+**Tier: 3**
+
+Apple visionOS targets:
+
+-   Apple visionOS on arm64
+-   Apple visionOS Simulator on arm64
+
+## Target maintainers
+
+-   [@agg23](https://github.com/agg23)
+
+## Requirements
+
+These targets are cross-compiled.
+To build these targets Xcode 15 or higher on macOS is required.
+
+## Building the target
+
+The targets can be built by enabling them for a `rustc` build, for example:
+
+```toml
+[build]
+build-stage = 1
+target = ["aarch64-apple-xros-sim"]
+```
+
+## Building Rust programs
+
+_Note: Building for this target requires the corresponding visionOS SDK, as provided by Xcode 15+._
+
+Rust programs can be built for these targets, if `rustc` has been built with support for them, for example:
+
+```text
+rustc --target aarch64-apple-xros-sim your-code.rs
+```
+
+## Testing
+
+There is no support for running the Rust testsuite on visionOS or the simulators.
+
+There is no easy way to run simple programs on visionOS or the visionOS simulators. Static library builds can be embedded into visionOS applications.
+
+## Cross-compilation toolchains and C code
+
+This target can be cross-compiled from x86_64 or aarch64 macOS hosts.
+
+Other hosts are not supported for cross-compilation, but might work when also providing the required Xcode SDK.