Add Besu Plugin information

docs/Concepts/Plugins.md

@@ -0,0 +1,48 @@
+description: Plugins
+<!--- END of page meta data -->
+
+# Plugins
+
+You can extend Hyperledger Besu functionality by building Java plugins. Use the
+Plugin API to take data from any Besu network, public or permissioned, and feed
+it into an application or system. 
+
+For example, create a plugin to add additional monitoring functionality or
+stream event data to a third-party application. The API exposes data about the
+following components:
+
+* Blocks
+* Balances
+* Transactions
+* Smart contracts
+* Execution results
+* Logs 
+* Syncing state
+
+![Besu Plugin API](../images/Hyperledger-Besu-Plugin-API.png)
+
+The Plugin API provides access to [interfaces](../Reference/Plugin-API-Interfaces.md) that allow you to build
+the plugin.
+
+!!! tip
+    View the [Plugin API webinar](https://youtu.be/78sa2WuA1rg) for an example of how to build a plugin.
+
+    The [Plugin API Javadoc](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/index.html) provides additional information about the available interfaces.
+
+## Install Plugins
+
+The plugin (`.jar`) must be copied to the `plugins` directory to allow Besu 
+access and use the plugin.
+
+!!! important
+    If not already present, the `plugins` directory must be created one directory
+    level below (`../`) the `besu` executable.
+
+Each plugin in the directory has the following lifecycle events:
+
+* **Register** - Executed when Besu starts. Besu checks plugin compatibility and registers plugins.
+* **Start** - Plugins are started after being successfully registered.
+* **Stop** - Plugins are stopped by Besu.
+
+!!! note
+    Besu does not guarantee the order plugins are called during lifecycle events. 

docs/Reference/Plugin-API-Interfaces.md

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+description: Plugin interfaces
+<!--- END of page meta data -->
+
+# Plugin API Interfaces
+
+API interfaces in Hyperledger Besu allow users to [build plugins](../Concepts/Plugins.md) to
+extend Besu functionality.
+
+The [Plugin API Javadoc](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/index.html) provides additional information about the available interfaces.
+
+## Core Plugin Classes
+
+The following interfaces provide core plugin classes.
+
+| Interface          | Description                                              |
+|--------------------|----------------------------------------------------------|
+| [**BesuContext**](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/org/hyperledger/besu/plugin/BesuContext.html)    | Allows plugins to access Besu services.  |
+| [**BesuPlugin**](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/org/hyperledger/besu/plugin/BesuPlugin.html)     | Used to manage the plugin lifecycle.  |
+
+
+## Plugin Services
+
+The following interfaces provide services that can be retrieved.
+
+| Interface          | Description                                              |
+|--------------------|----------------------------------------------------------|
+| [**BesuEvents**](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/org/hyperledger/besu/plugin/services/BesuEvents.html)     | Allows plugins to attach to various events during Besu operation.  |
+| [**BesuConfiguration**](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/org/hyperledger/besu/plugin/services/BesuConfiguration.html) | Provides file system locations of Besu's storage. |
+| [**IbftQueryService**](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/org/hyperledger/besu/plugin/services/query/IbftQueryService.html) | Allows IBFT 2.0 aspects of the blockchain to be queried. |
+| [**MetricCategoryRegistry**](https://javadoc.io/static/org.hyperledger.besu/plugin-api/1.3.4/org/hyperledger/besu/plugin/services/metrics/MetricCategoryRegistry.html) | Adds a new metrics category to the CLI. |
+| [**MetricsSystem**](https://javadoc.io/doc/org.hyperledger.besu/plugin-api/latest/org/hyperledger/besu/plugin/services/MetricsSystem.html)  | Register metrics with the Prometheus endpoint. |
+| [**PoaQueryService**](https://javadoc.io/static/org.hyperledger.besu/plugin-api/1.3.4/org/hyperledger/besu/plugin/services/query/PoaQueryService.html) | Query the current state of Clique and IBFT 2.0 consensus protocols. |       
+| [**PicoCLIOptions**](https://javadoc.io/static/org.hyperledger.besu/plugin-api/1.3.4/org/hyperledger/besu/plugin/services/PicoCLIOptions.html) | Adds CLI commands to the Besu command line.  |
+| [**StorageService**](https://javadoc.io/static/org.hyperledger.besu/plugin-api/1.3.4/org/hyperledger/besu/plugin/services/StorageService.html) | Allows plugins to register as a storage engine.  |
+
+To use the interfaces in your plugin, ensure the [Gradle build file](https://github.com/PegaSysEng/PluginsAPIDemo/blob/master/build.gradle) contains
+the `https://hyperledger-org.bintray.com/besu-repo` repository and the 
+`plugin-api` dependency.

docs/Reference/Resources.md

@@ -17,6 +17,8 @@ description: Hyperledger Besu resources including blog posts, webinars, and meet
 
 ## Webinars 
 
+[Besu Plugin API: Learn How to Leverage Plugin APIs on Hyperledger Besu](https://youtu.be/78sa2WuA1rg)
+
 [Permissioning in Blockchain: A Technical Look at Benefits and Best Practices](https://www.youtube.com/watch?v=CD0pHtNDqZs)
 
 [Privacy in Besu: How PegaSys Redefined Blockchain for Enterprises](https://www.youtube.com/watch?v=8l7SSZLyFL8)

mkdocs.yml

@@ -149,6 +149,7 @@ nav:
           - Overview: Concepts/Consensus-Protocols/Overview-Consensus.md
           - Comparing PoA Consensus Protocols: Concepts/Consensus-Protocols/Comparing-PoA.md
         - Client Libraries: Concepts/Client-Libraries.md
+        - Plugins: Concepts/Plugins.md
         - Privacy:
           - Overview: Concepts/Privacy/Privacy-Overview.md
           - Private Transactions: Concepts/Privacy/Private-Transactions.md
@@ -179,6 +180,7 @@ nav:
         - Besu API Objects: Reference/API-Objects.md
         - Genesis File Items: Reference/Config-Items.md
         - web3.js-eaa Methods: Reference/web3js-eea-Methods.md
+        - Plugin API Interfaces: Reference/Plugin-API-Interfaces.md
         - Accounts for Testing: Reference/Accounts-for-Testing.md
         - Security Disclosure Policy: Reference/Responsible-Disclosure.md
         - Blog Posts and Webinars: Reference/Resources.md