Add readme for path (#67)

* Add readme for path

* typo

README.md

@@ -46,6 +46,28 @@ Calling the generation with `--base_import_path=<somepath>/exampleoc` flag will
 
 The ygnmi client library uses the generated code to perform schema compliant subscriptions and set gNMI RPCs. 
 
+### gNMI path to ygnmi path
+
+ygnmi paths mimic with gNMI paths with a few transformations applied.
+
+1. Names are CamelCased: `network-instance` -> `NetworkInstance`
+2. YANG module names are omitted, and added to a root struct: `/openconfig-network-instance/network-interfaces/` -> `ocpath.Root().NetworkInstance()`
+3. Lists are compressed: `network-instances/network-instance[name=DEFAULT]` -> `NetworkInstance("DEFAULT")`
+4. List keys can be specified several ways:
+    1. Fully by specifying all keys: `protocols/protocol[identifier=BGP][name=test]` -> `Protocol(oc.PolicyTypes_INSTALL_PROTOCOL_TYPE_BGP, "test")`
+    2. Specifying no keys: `protocols/protocol[identifier=*][name=*]` -> `ProtocolAny()`
+    3. Specifying some keys: `protocols/protocol[identifier=BGP][name=*]` -> `ProtocolAny().WithIdentifier(oc.PolicyTypes_INSTALL_PROTOCOL_TYPE_BGP)`
+5. State or Config are specified at the end: `interface[name=eth0]/state/name` -> `Interface("eth0").Name().State()`
+
+Examples:
+
+|gNMI Path|ygnmi Call|
+|---------|----------|
+|`/network-instances/network-instance[name=DEFAULT]/protocols/protocol[identifier=BGP][name=test]/bgp/neighbors/neighbor[neighbor-address=localhost]/state/description`|`ocpath.Root().NetworkInstance("DEFAULT").Protocol(oc.PolicyTypes_INSTALL_PROTOCOL_TYPE_BGP, "test").Bgp().Neighbor("localhost").Description().State()`
+| `/interfaces/interface[name=*]/config/name` | `ocpath.Root().InterfaceAny().Name().Config()`
+
+Note: It is highly recommended to use this library with an IDE or autocomplete configured.
+
 ### Queries
 
 The ygnmi library uses generic queries to represent a gNMI path, the value type, and schema. Queries should never be constructed directly.