start with caches doc

docs/dev/ci/github_actions/caches.md

@@ -1,5 +1,102 @@
 # Overview of the Caches used in the OpenVINO GitHub Actions CI
 
+To speed up builds and tests and reduce network usage, OpenVINO workflows use caches.
+
 ## Available Caches
 
-## How to use Cache
+Three types of caches are available:
+* [GitHub Actions cache](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows)
+  * Available for both GitHub-hosted and self-hosted runners
+  * Accessible by `actions/cache` action
+  * Limited to 10 GB per repository
+  * Suitable for small dependencies caches and artefacts that could be reused between runs 
+* [Shared drive cache](#shared-drive-cache-usage-and-structure)
+  * Available only to the self-hosted runners
+  * Automatically available via a certain path
+  * Large storage
+  * Suitable for large caches
+    * e.g., build caches, models, datasets
+* Cloud storage via [Azure Blob Storage](https://azure.microsoft.com/en-us/products/storage/blobs)
+  * Available only to the self-hosted runners
+  * Used to cache and share build artefacts with [`sccache`](https://github.com/mozilla/sccache)
+
+The jobs in the workflows utilize appropriate caches based on job's needs.
+
+## GitHub Actions Cache
+
+This cache is used for sharing small dependencies or artefacts between runs. Refer to the [GitHub Actions official documentation](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows) for a complete reference.
+
+The `CPU functional tests` job in the `linux.yml` workflow uses this cache for sharing tests execution time to speed up the subsequent runs. First, the artefacts are saved with `actions/cache/save`:
+```yaml
+CPU_Functional_Tests:
+  name: CPU functional tests
+  ...
+  steps:
+    - name: Save tests execution time
+      uses: actions/cache/save@v3
+      if: github.ref_name == 'master'
+      with:
+        path: ${{ env.PARALLEL_TEST_CACHE }}
+        key: ${{ runner.os }}-${{ runner.arch }}-tests-functional-cpu-stamp-${{ github.sha }}
+    ...
+```
+with a particular key: `${{ runner.os }}-${{ runner.arch }}-tests-functional-cpu-stamp-${{ github.sha }}`. Then it could be seen in the [repository's cache](https://github.com/openvinotoolkit/openvino/actions/caches):
+![gha_cache_example](../../../sphinx_setup/_static/images/ci/gha_cache_example.png)
+
+The next runs could download the artefact from the repository's cache with `actions/cache/restore` and use it:
+```yaml
+CPU_Functional_Tests:
+  name: CPU functional tests
+  ...
+  steps:
+    - name: Restore tests execution time
+      uses: actions/cache/restore@v3
+      with:
+        path: ${{ env.PARALLEL_TEST_CACHE }}
+        key: ${{ runner.os }}-${{ runner.arch }}-tests-functional-cpu-stamp-${{ github.sha }}
+        restore-keys: |
+          ${{ runner.os }}-${{ runner.arch }}-tests-functional-cpu-stamp
+    ...
+```
+The `restore-keys` key is used to find the needed cache entry. `actions/cache` searches for the full or partial match and downloads the found cache to the provided `path`.
+
+Refer to the [`actions/cache`'s documentation](https://github.com/actions/cache) for a complete syntax reference.
+
+## Shared Drive Cache Usage and Structure
+
+**Note**: This cache is enable for [self-hosted runners](./runners.md) only.
+
+## Cloud Storage via Azure Blob Storage
+
+This cache is used for sharing OpenVINO build artefacts between runs. 
+The [`sccache`](https://github.com/mozilla/sccache) tool can cache, upload and download build files to/from [Azure Blob Storage](https://azure.microsoft.com/en-us/products/storage/blobs).
+
+**Note**: This cache is enable for [self-hosted runners](./runners.md) only.
+
+`sccache` needs several things to work:
+* be installed
+* credential environment variables: `SCCACHE_AZURE_BLOB_CONTAINER`, `SCCACHE_AZURE_CONNECTION_STRING`
+  * They are already set up on the self-hosted runners
+  * They could be passed to a Docker containers via the `options` key under the `container` key. See the example below
+* `SCCACHE_AZURE_KEY_PREFIX` environment variable - essentially the folder where the cache for this OS/architecture will be saved
+* `CMAKE_CXX_COMPILER_LAUNCHER` and `CMAKE_C_COMPILER_LAUNCHER` environment variables to enable `sccache` for caching C++/C build files
+
+### `sccache` Installation
+
+The installation is done via the community-provided `mozilla-actions/sccache-action` action:
+```yaml
+- name: Install sccache
+  uses: mozilla-actions/[email protected]
+  with:
+    version: "v0.5.4"
+```
+
+This step should be placed somewhere in the workflow **before** the build step.
+
+### Passing Credential Environment Variables
+
+If a job is running outside a container, the 
+
+### Providing `sccache` Prefix
+
+### Enabling `sccache` for 

docs/dev/ci/github_actions/overview.md

@@ -246,20 +246,12 @@ The jobs in the workflows utilize appropriate Docker images based on a job's nee
 
 ## Caches
 
-There are two types of caches available:
+Three types of caches are available:
 * [GitHub Actions cache](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows)
-  * Accessible by `actions/cache` action
-  * Available both GitHub-hosted and self-hosted runners
-  * Limited to 10GB per repository
-  * Suitable for small dependencies caches and artefacts that could be reused between runs 
 * Shared drive cache
-  * Mounted into the Docker container
-  * Available only to the self-hosted runners
-  * Large storage
-  * Suitable for large caches
-    * e.g., build caches, models, datasets
+* Remote build cache via [Azure Blob Storage](https://azure.microsoft.com/en-us/products/storage/blobs)
 
-The jobs in the workflows utilize appropriate caches based on a job's needs. Read more about the available caches and how to choose one [here](./caches.md).
+The jobs in the workflows utilize appropriate caches based on job's needs. Read more about the available caches and how to use one [here](./caches.md).
 
 ## Adding New Tests