add instruction for adding a new domain

interface/README.md

@@ -0,0 +1,36 @@
+# RPC Types
+1. Types that implements `core::marker::Copy` trait beside function pointers
+
+# Interface syntax.
+## RPC
+See [RPC Types](#rpc_types) for valid RPC Types.
+```
+#[interface]
+pub trait YourInterface {
+    fn method_name(&self, [arg: RPCType],*) -> RpcResult<RPCType>;
+    ... more methods ...
+}
+```
+
+
+# How to add a new domain.
+1. Add a domain create interface inside of the `domain_create` module.
+    ```
+        #[domain_create(path = "my_domain_name")]
+        pub trait CreateYourDomain: Send + Sync {
+            fn create_domain_your_domain(&self) -> (Box<dyn Domain>, Box<dyn YourDomain>);
+        }
+    ```
+1. Add it inside of `interface::proxy::Proxy` as a method of the proxy.
+    ```
+        fn as_domain_create_CreateDomC1(&self) -> Arc<dyn crate::domain_create::CreateDomC1>;
+    ```
+1. Update the proxy object instantiation in _domains/usr/proxy/src/main.rs:trusted\_entry_ so the 
+    proxy will contain an instance of `CreateYourDomain`.
+1. Update the proxy domain entry point in both `interface::domain_create::CreateProxy` and 
+    _domains/usr/proxy/src/main.rs:trusted\_entry_ to allow the instance of `CreateYourDomain` be 
+    passed down from domain `redleaf_init` to domain `proxy`.
+1. Update the entry point and the instantiation of the proxy domain of `redleaf_init` in 
+    _domains/sys/init/src/main.rs:trusted\_entry_. Make sure the signature of the entry point is
+    the same as the one _kernel/src/generated\_domain\_create.rs:create\_domain\_init_
+