Document Soong namespaces

Bug: 65683273
Test: Read README.md

Change-Id: I179c085e123858ae425515ac6bbf4b272c245a2e

README.md

@@ -95,6 +95,38 @@ cc_binary {
 }
 ```
 
+### Name resolution
+
+Soong provides the ability for modules in different directories to specify
+the same name, as long as each module is declared within a separate namespace.
+A namespace can be declared like this:
+
+```
+soong_namespace {
+    imports: ["path/to/otherNamespace1", "path/to/otherNamespace2"],
+}
+```
+
+Each Soong module is assigned a namespace based on its location in the tree.
+Each Soong module is considered to be in the namespace defined by the
+soong_namespace found in an Android.bp in the current directory or closest
+ancestor directory, unless no such soong_namespace module is found, in which
+case the module is considered to be in the implicit root namespace.
+
+When Soong attempts to resolve dependency D declared my module M in namespace
+N which imports namespaces I1, I2, I3..., then if D is a fully-qualified name
+of the form "//namespace:module", only the specified namespace will be searched
+for the specified module name. Otherwise, Soong will first look for a module
+named D declared in namespace N. If that module does not exist, Soong will look
+for a module named D in namespaces I1, I2, I3... Lastly, Soong will look in the
+root namespace.
+
+Until we have fully converted from Make to Soong, it will be necessary for the
+Make product config to specify a value of PRODUCT_SOONG_NAMESPACES. Its value
+should be a space-separated list of namespaces that Soong export to Make to be
+built by the `m` command. After we have fully converted from Make to Soong, the
+details of enabling namespaces could potentially change.
+
 ### Formatter
 
 Soong includes a canonical formatter for blueprint files, similar to