Document multiple providers support

Author: alexander-demicev

docs/book/src/SUMMARY.md

@@ -36,6 +36,7 @@
             - [Implementing Topology Mutation Hook Extensions](./tasks/experimental-features/runtime-sdk/implement-topology-mutation-hook.md)
             - [Deploying Runtime Extensions](./tasks/experimental-features/runtime-sdk/deploy-runtime-extension.md)
         - [Ignition Bootstrap configuration](./tasks/experimental-features/ignition.md)
+    - [Running multiple providers](./tasks/multiple-providers.md)
 - [Security Guidelines](./security/index.md)
     - [Pod Security Standards](./security/pod-security-standards.md)
 - [clusterctl CLI](./clusterctl/overview.md)

docs/book/src/tasks/multiple-providers.md

@@ -0,0 +1,14 @@
+# Running multiple providers
+
+Cluster API supports running multiple infrastructure/bootstrap/control plane providers on the same management cluster. It's highly recommeded to rely on
+[clusterctl init](../clusterctl/commands/init.md) command in this case. [clusterctl](../clusterctl/overview.md) will help ensure that all providers support the same
+[API Version of Cluster API](../clusterctl/provider-contract.md#metadata-yaml) (contract).
+
+<aside class="note warning">
+
+<h1>Warning</h1>
+
+Currently, the case of running multiple providers is not covered in Cluster API E2E test suite. It's recommended to set up a custom validation pipeline of
+your specific combination of providers before deploying it on a production environment.
+
+</aside>