diff --git a/src/parser_internal.h b/src/parser_internal.h
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+/**
+ * @file parser_internal.h
+ * @author Radek Krejci <rkrejci@cesnet.cz>
+ * @brief Internal structures and functions for libyang parsers
+ *
+ * Copyright (c) 2020 CESNET, z.s.p.o.
+ *
+ * This source code is licensed under BSD 3-Clause License (the "License").
+ * You may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://opensource.org/licenses/BSD-3-Clause
+ */
+
+#ifndef LY_PARSER_INTERNAL_H_
+#define LY_PARSER_INTERNAL_H_
+
+#include "parser.h"
+#include "tree_schema_internal.h"
+
+/**
+ * @brief Parser input structure specifying where the data are read.
+ */
+struct ly_in {
+    LY_IN_TYPE type;     /**< type of the output to select the output method */
+    const char *current;
+    const char *start;
+    size_t length;
+    union {
+        int fd;          /**< file descriptor for LY_IN_FD type */
+        FILE *f;         /**< file structure for LY_IN_FILE and LY_IN_FILEPATH types */
+        struct {
+            int fd;      /**< file descriptor for LY_IN_FILEPATH */
+            char *filepath;   /**< stored original filepath */
+        } fpath;         /**< filepath structure for LY_IN_FILEPATH */
+    } method;            /**< type-specific information about the output */
+};
+
+/**
+ * @brief Parse submodule from YANG data.
+ * @param[in,out] ctx Parser context.
+ * @param[in] ly_ctx Context of YANG schemas.
+ * @param[in] main_ctx Parser context of main module.
+ * @param[in] data Input data to be parsed.
+ * @param[out] submod Pointer to the parsed submodule structure.
+ * @return LY_ERR value - LY_SUCCESS, LY_EINVAL or LY_EVALID.
+ */
+LY_ERR yang_parse_submodule(struct lys_yang_parser_ctx **context, struct ly_ctx *ly_ctx, struct lys_parser_ctx *main_ctx,
+                            const char *data, struct lysp_submodule **submod);
+
+/**
+ * @brief Parse module from YANG data.
+ * @param[in] ctx Parser context.
+ * @param[in] data Input data to be parsed.
+ * @param[in, out] mod Prepared module structure where the parsed information, including the parsed
+ * module structure, will be filled in.
+ * @return LY_ERR value - LY_SUCCESS, LY_EINVAL or LY_EVALID.
+ */
+LY_ERR yang_parse_module(struct lys_yang_parser_ctx **context, const char *data, struct lys_module *mod);
+
+/**
+ * @brief Parse module from YIN data.
+ *
+ * @param[in,out] yin_ctx Context created during parsing, is used to finalize lysp_model after it's completly parsed.
+ * @param[in] data Input data to be parsed.
+ * @param[in,out] mod Prepared module structure where the parsed information, including the parsed
+ * module structure, will be filled in.
+ *
+ * @return LY_ERR values.
+ */
+LY_ERR yin_parse_module(struct lys_yin_parser_ctx **yin_ctx, const char *data, struct lys_module *mod);
+
+/**
+ * @brief Parse submodule from YIN data.
+ *
+ * @param[in,out] yin_ctx Context created during parsing, is used to finalize lysp_model after it's completly parsed.
+ * @param[in] ctx Libyang context.
+ * @param[in] main_ctx Parser context of main module.
+ * @param[in,out] data Input data to be parsed.
+ * @param[in,out] submod Submodule structure where the parsed information, will be filled in.
+ * @return LY_ERR values.
+ */
+LY_ERR yin_parse_submodule(struct lys_yin_parser_ctx **yin_ctx, struct ly_ctx *ctx, struct lys_parser_ctx *main_ctx,
+                           const char *data, struct lysp_submodule **submod);
+
+#endif /* LY_PARSER_INTERNAL_H_ */