Add docs for RSocket interface client

Closes gh-24456

Author: rstoyanchev

src/docs/asciidoc/integration.adoc

@@ -364,7 +364,7 @@ If necessary the `Content-Type` may also be set explicitly.
 
 
 [[rest-http-interface]]
-=== HTTP Interface
+  === HTTP Interface
 
 The Spring Framework lets you define an HTTP service as a Java interface with annotated
 methods for HTTP exchanges. You can then generate a proxy that implements this interface
@@ -422,7 +422,7 @@ method parameters:
 
 [cols="1,2", options="header"]
 |===
-| Controller method argument | Description
+| Method argument | Description
 
 | `URI`
 | Dynamically set the URL for the request, overriding the annotation's `url` attribute.
@@ -469,7 +469,7 @@ Annotated, HTTP exchange methods support the following return values:
 
 [cols="1,2", options="header"]
 |===
-| Controller method return value | Description
+| Method return value | Description
 
 | `void`, `Mono<Void>`
 | Perform the given request, and release the response content, if any.

src/docs/asciidoc/rsocket.adoc

@@ -904,3 +904,82 @@ simply use a callback to customize registrations as follows:
 			}
 			.build()
 ----
+
+
+
+
+[[rsocket-interface]]
+== RSocket Interface
+
+The Spring Framework lets you define an RSocket service as a Java interface with annotated
+methods for RSocket exchanges. You can then generate a proxy that implements this interface
+and performs the exchanges. This helps to simplify RSocket remote access by wrapping the
+use of the underlying <<rsocket-requester>>.
+
+One, declare an interface with `@RSocketExchange` methods:
+
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+	interface RadarService {
+
+		@RSocketExchange("radars")
+		Flux<AirportLocation> getRadars(@Payload MapRequest request);
+
+		// more RSocket exchange methods...
+
+	}
+----
+
+Two, create a proxy that will perform the declared RSocket exchanges:
+
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+	RSocketRequester requester = ... ;
+	RSocketServiceProxyFactory factory = new RSocketServiceProxyFactory(requester);
+	factory.afterPropertiesSet();
+
+	RepositoryService service = factory.createClient(RadarService.class);
+----
+
+
+[[rsocket-interface-method-parameters]]
+=== Method Parameters
+
+Annotated, RSocket exchange methods support flexible method signatures with the following
+method parameters:
+
+[cols="1,2", options="header"]
+|===
+| Method argument | Description
+
+| `@DestinationVariable`
+| Add a route variable to pass to `RSocketRequester` along with the route from the
+  `@RSocketExchange` annotation in order to expand template placeholders in the route.
+  This variable can be a String or any Object, which is then formatted via `toString()`.
+
+| `@Payload`
+| Set the input payload(s) for the request. This can be a concrete value, or any producer
+  of values that can be adapted to a Reactive Streams `Publisher` via
+  `ReactiveAdapterRegistry`
+
+| `Object`, if followed by `MimeType`
+| The value for a metadata entry in the input payload. This can be any `Object` as long
+  as the next argument is the metadata entry `MimeType`. The value can be can a concrete
+  value or any producer of a single value that can be adapted to a Reactive Streams
+  `Publisher` via `ReactiveAdapterRegistry`.
+
+| `MimeType`
+| The `MimeType` for a metadata entry. The preceding method argument is expected to be
+  the metadata value.
+
+|===
+
+
+[[rsocket-interface-return-values]]
+=== Return Values
+
+Annotated, RSocket exchange methods support return values that are concrete value(s), or
+any producer of value(s) that can be adapted to a Reactive Streams `Publisher` via
+`ReactiveAdapterRegistry`.
+
+