Update information on WebApplicationContext hierarchy

Issue: SPR-16041

src/docs/asciidoc/web/webflux.adoc

@@ -346,8 +346,13 @@ server.addConnector(connector);
 server.start();
 ----
 
-You can also deploy as a WAR to any Servlet 3.1 container by wrapping the handler with
-`ServletHttpHandlerAdapter` as a `Servlet`.
+[NOTE]
+====
+To deploy as a WAR to a Servlet 3.1+ container, wrap `HttpHandler` with
+`ServletHttpHandlerAdapter` and register that as a `Servlet`. Use
+{api-spring-framework}/web/reactive/support/AbstractServletHttpHandlerAdapterInitializer.html[AbstractServletHttpHandlerAdapterInitializer]
+to automate the required Servlet container configuration.
+====
 
 
 

src/docs/asciidoc/web/webmvc.adoc

@@ -161,6 +161,12 @@ Below is example configuration with a `WebApplicationContext` hierarchy:
   }
 ----
 
+[TIP]
+====
+If an application context hierarchy is not required, applications may return all
+configuration via `getRootConfigClasses()` and `null` from `getServletConfigClasses()`.
+====
+
 And the `web.xml` equivalent:
 
 [source,xml,indent=0]
@@ -195,6 +201,13 @@ And the `web.xml` equivalent:
 </web-app>
 ----
 
+[TIP]
+====
+If an application context hierarchy is not required, applications may configure a
+"root" context only and leave the `contextConfigLocation` Servlet parameter empty.
+====
+
+
 
 
 [[mvc-servlet-special-bean-types]]