docs: clarify how extensions work

Fixes: fb60895 Allow getting module extensions
Change-Id: I49a69608243c4ceb95736ed66c4ce891ba106815

Author: jktjkt

include/libyang-cpp/Module.hpp

@@ -156,7 +156,7 @@ class LIBYANG_CPP_EXPORT Identity {
 /**
  * @brief Contains information about compiled extension.
  *
- * Wraps `lysc_extension_instance`
+ * Wraps `lysc_ext_instance`
  */
 class LIBYANG_CPP_EXPORT ExtensionInstance {
 public:

src/Module.cpp

@@ -391,7 +391,11 @@ ExtensionInstance::ExtensionInstance(const lysc_ext_instance* ext, std::shared_p
 }
 
 /**
- * @brief Returns the argument
+ * @brief Returns the argument name
+ *
+ * As an example, the RESTCONF RFC defines an extension named "yang-data".
+ * This extension is then instantiated at two places by that RFC, under
+ * names "yang-errors" and "yang-api".
  *
  * Wraps `lysc_ext_instance::argument`.
  */
@@ -417,7 +421,7 @@ Extension::Extension(const lysc_ext* ext, std::shared_ptr<ly_ctx> ctx)
 }
 
 /**
- * @brief Returns the name of the module.
+ * @brief Returns the name of the extension definition
  *
  * Wraps `lysc_ext::name`.
  */