Function ly_ctx_get_submodule 

pub unsafe extern "C" fn ly_ctx_get_submodule(
    ctx: *const ly_ctx,
    submodule: *const c_char,
    revision: *const c_char,
) -> *const lysp_submodule

@brief Get a specific submodule from context. If its belongs-to module is known, use ::ly_ctx_get_submodule2().

@param[in] ctx libyang context to search in. @param[in] submodule Submodule name to find. @param[in] revision Revision of the submodule to find, NULL for a submodule without a revision. @return Found submodule, NULL if there is none.