Consolidate contributing guide (#20590)

* Consolidate contributing guide

* Delete depreacated doc

Author: raych1

CONTRIBUTING.md

@@ -11,18 +11,19 @@ This file provides general guidance for developers that are creating or updating
 
 <!-- toc -->
 
-- [Reporting problems](#reporting-problems)
+- [Reporting Problems](#reporting-problems)
 - [Avoid Breaking Changes](#avoid-breaking-changes)
 - [Design Guidelines](#design-guidelines)
-  * [Exceptions for consistency within a service](#exceptions-for-consistency-within-a-service)
+  * [Exceptions for Consistency within a Service](#exceptions-for-consistency-within-a-service)
 - [Coding Style](#coding-style)
 - [Directory Structure](#directory-structure)
 - [Pull Requests](#pull-requests)
-- [Pull Request checks](#pull-request-checks)
+- [Pull Request Checks](#pull-request-checks)
+- [Internal Contribution Guide](#internal-contribution-guide)
 
 <!-- tocstop -->
 
-## Reporting problems
+## Reporting Problems
 
 If you discover a problem with a REST API document in this repo, feel free to [open an issue](https://github.com/Azure/azure-rest-api-specs/issues/new). But please do not report issues with service behavior / functionality in this repo.
 
@@ -40,7 +41,7 @@ There is a [YouTube video series](https://www.youtube.com/watch?v=9Ng00IlBCtw) b
 
 Another resource is the [Considerations for Service Design](https://github.com/microsoft/api-guidelines/blob/vNext/azure/ConsiderationsForServiceDesign.md), which is an introduction to REST API design mainly for services that are just getting started.
 
-### Exceptions for consistency within a service
+### Exceptions for Consistency within a Service
 
 There are situations where a service has GA'd their API with design patterns that do not follow our guidelines and it would be a breaking change to adopt the API design in the guidelines.
 Because the first rule is to avoid breaking changes and because we want APIs to be consistent within a service, these design patterns are considered the standard for that service and should be followed in all subsequent (non-breaking) versions of that service's REST API.
@@ -70,7 +71,7 @@ If you want to contribute to the repository, follow these steps:
 
 Microsoft employees can try out the experience at [OpenAPI Hub](https://aka.ms/openapihub) for [adding a new API version using OpenAPI Hub](https://dev.azure.com/azure-sdk/internal/_wiki/wikis/internal.wiki/208/OpenAPI-Hub-Adding-new-API-version).
 
-## Pull Request checks
+## Pull Request Checks
 
 Every PR in this repo will go through a series of PR checks, including:
 
@@ -90,3 +91,10 @@ Every PR in this repo will go through a series of PR checks, including:
 
 When any of these PR checks fails it will post a comment to the PR with links to information on how to resolve the problem.
 There is also the [CI Fix Guide](https://aka.ms/ci-fix) that describes how to fix common PR check failures.
+
+## Internal Contribution Guide
+For management plane, please refer to https://aka.ms/rpguidelines; 
+
+For data-plane, please refer to [Guide to design and creation of Data Plane REST API and Client Libraries](https://dev.azure.com/azure-sdk/internal/_wiki/wikis/internal.wiki/591/Guide-to-design-and-creation-of-Data-Plane-REST-API-and-Client-Libraries); 
+
+For contribution access to spec repos, please refer to [Public repo vs. Private repo: To get write access](https://dev.azure.com/azure-sdk/internal/_wiki/wikis/internal.wiki/202/Overall-Process-of-Management-Plane-SDK-Onboarding?anchor=2.-create/update-the-openapi-specifications%2C-and-launch-swagger-pr-review)