> myBook.tex
> myBook_structure.tex

> part1_Introduction
    |
    |--- Introduction_to_FreeRTOS
    |       |-- someFile.tex
    |       '-- someFile.tex
    |
    '--- How_to_use_FreeRTOS
            |-- someFile.tex
            '-- someFile.tex

> part2_FreeRTOS_examples
    |
    |--- First_example
    |       |-- someFile.tex
    |       '-- someFile.tex
    |
    '--- Second_Example
            |-- someFile.tex
            '-- someFile.tex
...

%% myBook_structure.tex
    %% --------------------
    defpart1ch1{./part1_Introduction/Introduction_to_FreeRTOS}
    defpart1ch2{./part1_Introduction/How_to_use_FreeRTOS}
    defpart2ch1{./part2_FreeRTOS_examples/First_example}
    defpart2ch2{./part2_FreeRTOS_examples/Second_example}
    ...

%% myBook.tex
    %% -----------

    input{./myBook_structure}
    ..
    begin{document}
        ..
        %% Include a file from chapter 1 within part 1:
        include{part1ch1/someFile}
        %% Include a file from chapter 2 within part 1:
        include{part1ch2/someFile}
        ..
    end{document}

%% myBook_structure.tex
    %% --------------------
    defpart1ch1{./part1_Introduction/FreeRTOS_intro} %% <- this line changed
    defpart1ch2{./part1_Introduction/How_to_use_FreeRTOS}
    ... all other lines remain the same