Fix doc links (pytorch#16847)

Author: rascani

CONTRIBUTING.md

@@ -26,7 +26,7 @@ executorch
 │   ├── <a href="backends/apple">apple</a> - Apple-specific backends.
 │   │   ├── <a href="backends/apple/coreml">coreml</a> - CoreML backend for Apple devices. See <a href="docs/source/backends/coreml/coreml-overview.md">doc</a>.
 │   │   └── <a href="backends/apple/mps">mps</a> - Metal Performance Shaders backend for Apple devices. See <a href="docs/source/backends/mps/mps-overview.md">doc</a>.
-│   ├── <a href="backends/arm">arm</a> - ARM architecture backends. See <a href="docs/source/backends-arm-ethos-u.md">doc</a>.
+│   ├── <a href="backends/arm">arm</a> - ARM architecture backends. See <a href="docs/source/backends/arm-ethos-u/arm-ethos-u-overview.md">doc</a>.
 │   ├── <a href="backends/cadence">cadence</a> - Cadence-specific backends. See <a href="docs/source/backends-cadence.md">doc</a>.
 │   ├── <a href="backends/example">example</a> - Example backend implementations.
 │   ├── <a href="backends/mediatek">mediatek</a> - MediaTek-specific backends. See <a href="docs/source/backends-mediatek.md">doc</a>.

examples/README.md

@@ -34,7 +34,7 @@ A user's journey may commence by exploring the demos located in the [`portable/`
 
 ## Demos Apps
 
-Explore mobile apps with ExecuTorch models integrated and deployable on [Android](demo-apps/android) and [iOS](https://github.com/meta-pytorch/executorch-examples/tree/main/llm/apple). This provides end-to-end instructions on how to export Llama models, load on device, build the app, and run it on device.
+Explore mobile apps with ExecuTorch models integrated and deployable on [Android](https://github.com/meta-pytorch/executorch-examples/tree/main/llm/android) and [iOS](https://github.com/meta-pytorch/executorch-examples/tree/main/llm/apple). This provides end-to-end instructions on how to export Llama models, load on device, build the app, and run it on device.
 
 For specific details related to models and backend, you can explore the various subsections.
 

examples/arm/ethos-u-porting-guide.md

@@ -1,6 +1,6 @@
 # Introduction
 
-As you have seen in in the [Arm® Ethos™-U NPU backend tutorial](../../docs/source/backends-arm-ethos-u.md), ExecuTorch has two distinct parts:
+As you have seen in in the [Arm® Ethos™-U NPU backend tutorial](../../docs/source/backends/arm-ethos-u/tutorials/ethos-u-getting-started.md), ExecuTorch has two distinct parts:
 - Ahead-of-time(AoT) compile flow
 - Ethos-U on-device runtime