sdk.name for hybrid sdks (#832)

* sdk.name for hybrid sdks

* Apply suggestions from code review

Author: bruno-garcia

src/docs/sdk/event-payloads/sdk.mdx

@@ -19,6 +19,24 @@ ecosystem. Official Sentry SDKs use the _entity_ `sentry`. Examples:
 - `sentry.python`
 - `sentry.javascript.react-native`
 
+For SDKs that are composed of more than one Sentry SDK. For example, [the Unity SDK](https://github.com/getsentry/sentry-unity/issues/616)
+which includes a .NET layer as well as different native layers. When events come out
+of the native layer, it's important to distinguish from the stand-alone native SDK.
+We do that by appending the top SDK to the end of the native SDK name. Examples:
+
+Unity SDK:
+
+- `sentry.dotnet.unity` on events coming from C#. As based on the spec above.
+  - `sentry.java.android.unity` on for events of the Java layer on Android
+  - `sentry.native.android.unity` on for events of the Native layer on Android
+  - `sentry.cocoa.unity` on for events from iOS/macOS layer
+  - `sentry.native.unity` on for events coming from `sentry.native` directly. Such as on Windows and Linux.
+
+Android SDK
+
+- `sentry.java.android` on events from the Java layer. Since the Android SDK is based on the Java SDK.
+- `sentry.native.android` on events from NDK. It's `sentry.native` but it's bundled in the Android SDK with some customization.
+
 `version`
 
 : **Required**. The version of the SDK. It should have the [Semantic