tree schema CHANGE support extension instances in simple text statements
diff --git a/src/tree_schema.h b/src/tree_schema.h
index 80313f4..3aa4b5d 100644
--- a/src/tree_schema.h
+++ b/src/tree_schema.h
@@ -84,11 +84,63 @@
 };
 
 /**
+ * @brief Enum of substatements in which extension instances can appear.
+ */
+typedef enum {
+    LYEXT_SUBSTMT_SELF = 0,      /**< extension of the structure itself, not substatement's */
+    LYEXT_SUBSTMT_ARGUMENT,      /**< extension of the argument statement, can appear in lys_ext */
+    LYEXT_SUBSTMT_BASE,          /**< extension of the base statement, can appear (repeatedly) in lys_type and lys_ident */
+    LYEXT_SUBSTMT_BELONGSTO,     /**< extension of the belongs-to statement, can appear in lys_submodule */
+    LYEXT_SUBSTMT_CONTACT,       /**< extension of the contact statement, can appear in lys_module */
+    LYEXT_SUBSTMT_DEFAULT,       /**< extension of the default statement, can appear in lys_node_leaf, lys_node_leaflist,
+                                      lys_node_choice and lys_deviate */
+    LYEXT_SUBSTMT_DESCRIPTION,   /**< extension of the description statement, can appear in lys_module, lys_submodule,
+                                      lys_node, lys_import, lys_include, lys_ext, lys_feature, lys_tpdf, lys_restr,
+                                      lys_ident, lys_deviation, lys_type_enum, lys_type_bit, lys_when and lys_revision */
+    LYEXT_SUBSTMT_ERRTAG,        /**< extension of the error-app-tag statement, can appear in lys_restr */
+    LYEXT_SUBSTMT_ERRMSG,        /**< extension of the error-message statement, can appear in lys_restr */
+    LYEXT_SUBSTMT_KEY,           /**< extension of the key statement, can appear in lys_node_list */
+    LYEXT_SUBSTMT_NAMESPACE,     /**< extension of the namespace statement, can appear in lys_module */
+    LYEXT_SUBSTMT_ORGANIZATION,  /**< extension of the organization statement, can appear in lys_module and lys_submodule */
+    LYEXT_SUBSTMT_PATH,          /**< extension of the path statement, can appear in lys_type */
+    LYEXT_SUBSTMT_PREFIX,        /**< extension of the prefix statement, can appear in lys_module, lys_submodule (for
+                                      belongs-to's prefix) and lys_import */
+    LYEXT_SUBSTMT_PRESENCE,      /**< extension of the presence statement, can appear in lys_node_container */
+    LYEXT_SUBSTMT_REFERENCE,     /**< extension of the reference statement, can appear in lys_module, lys_submodule,
+                                      lys_node, lys_import, lys_include, lys_revision, lys_tpdf, lys_restr, lys_ident,
+                                      lys_ext, lys_feature, lys_deviation, lys_type_enum, lys_type_bit and lys_when */
+    LYEXT_SUBSTMT_REVISIONDATE,  /**< extension of the revision-date statement, can appear in lys_import and lys_include */
+    LYEXT_SUBSTMT_UNITS,         /**< extension of the units statement, can appear in lys_tpdf, lys_node_leaf,
+                                      lys_node_leaflist and lys_deviate */
+    LYEXT_SUBSTMT_VALUE,         /**< extension of the value statement, can appear in lys_type_enum */
+    LYEXT_SUBSTMT_VERSION,       /**< extension of the yang-version statement, can appear in lys_module and lys_submodule */
+    LYEXT_SUBSTMT_MODIFIER,      /**< extension of the modifier statement, can appear in lys_restr */
+    LYEXT_SUBSTMT_REQINSTANCE,   /**< extension of the require-instance statement, can appear in lys_type */
+    LYEXT_SUBSTMT_YINELEM,       /**< extension of the yin-element statement, can appear in lys_ext */
+    LYEXT_SUBSTMT_CONFIG,        /**< extension of the config statement, can appear in lys_node and lys_deviate */
+    LYEXT_SUBSTMT_MANDATORY,     /**< extension of the mandatory statement, can appear in lys_node_leaf, lys_node_choice,
+                                      lys_node_anydata and lys_deviate */
+    LYEXT_SUBSTMT_ORDEREDBY,     /**< extension of the ordered-by statement, can appear in lys_node_list and lys_node_leaflist */
+    LYEXT_SUBSTMT_STATUS,        /**< extension of the status statement, can appear in lys_tpdf, lys_node, lys_ident,
+                                      lys_ext, lys_feature, lys_type_enum and lys_type_bit */
+    LYEXT_SUBSTMT_DIGITS,        /**< extension of the fraction-digits statement, can appear in lys_type */
+    LYEXT_SUBSTMT_MAX,           /**< extension of the max-elements statement, can appear in lys_node_list,
+                                      lys_node_leaflist and lys_deviate */
+    LYEXT_SUBSTMT_MIN,           /**< extension of the min-elements statement, can appear in lys_node_list,
+                                      lys_node_leaflist and lys_deviate */
+    LYEXT_SUBSTMT_POSITION,      /**< extension of the position statement, can appear in lys_type_bit */
+    LYEXT_SUBSTMT_UNIQUE,        /**< extension of the unique statement, can appear in lys_node_list and lys_deviate */
+} LYEXT_SUBSTMT;
+
+/**
  * @brief YANG extension instance
  */
 struct lysp_ext_instance {
     const char *name;                /**< extension identifier, including possible prefix */
     const char *argument;            /**< optional value of the extension's argument */
+    LYEXT_SUBSTMT insubstmt;         /**< value identifying placement of the extension instance */
+    uint32_t insubstmt_index;        /**< in case the instance is in a substatement, this identifies
+                                          the index of that substatement */
     struct lysp_stmt *children;      /**< list of the extension's substatements (linked list) */
 };