Prepare a simple TOC for 4/2 launch. (#2728)

Summary:
Pull Request resolved: #2728

I think the current TOC contains more information that would be later populated after 4/2.

I simplified the current TOC to be one page and reflecting current blockers for 4/2 launch. We can always venture out to more pages, but let's start with a simple single page.

Reviewed By: dbort

Differential Revision: D55451176

fbshipit-source-id: dc49460fdfbaa0f9b242671b3c9a69e412b1b899

Author: mergennachin

docs/source/index.rst

@@ -85,10 +85,7 @@ Topics in this section will help you get started with ExecuTorch.
    :caption: Working with LLMs
    :hidden:
 
-   llm/introduction
-   llm/mobile/index
-   llm/desktop/index
-   llm/advanced-flow/index
+   llm/getting-started
 
 .. toctree::
    :glob:

docs/source/llm/advanced-flow/advanced-flow.md

@@ -0,0 +1,34 @@
+# Getting Started with LLMs via ExecuTorch
+
+This section provides guidance on enabling Large Language Models (LLMs), starting with a simple example and gradually introducing new concepts to improve performance and productivity.
+
+## Prerequisites
+
+- To run this tutorial, you’ll first need to first [Set up your ExecuTorch environment](../getting-started-setup.md).
+
+- We highly suggest you to check out [LLama2 README](../../../examples/models/llama2/README.md) in our examples for end-to-end Llama2 mobile demo.
+
+
+## Simple “Hello World” LLM example
+
+Let's create a simple LLM app from scratch. TODO
+
+## Quantization
+
+Most LLMs are too large to fit into a mobile phone, making quantization necessary. In this example, we will demonstrate how to use the XNNPACKQuantizer to quantize the model and run it on a CPU. TODO
+
+## Use Mobile Acceleration
+
+One of the benefits of ExecuTorch is the ability to delegate to mobile accelerators. Now, we will show a few examples of how to easily take advantage of mobile accelerators. TODO
+
+## Debugging and Profiling
+
+It is sometimes necessary to profile and inspect the execution process. In this example, we will demonstrate how the ExecuTorch SDK can be used to identify which operations are being executed on which hardware.  TODO
+
+## How to use custom kernels
+
+In some cases, it is necessary to write custom kernels or import them from another source in order to achieve the desired performance. In this example, we will demonstrate how to use the `kvcache_with_sdpa` kernel.
+
+## How to build Mobile Apps
+
+Here's how to finally build a mobile app on Android and iOS. TODO