\documentclass[a4paper,10pt]{article}

\input{preamble.tex}

\usepackage{subfiles}
\begin{document}

\titleformat{\part}[display]
    {\Huge\scshape\filright}
    {\partname~\thepart:}
    {20pt}
    {\makeatother}

\tableofcontents
\let\tableofcontents\relax

\newpage

\subfile{vhdl_intro/vhdl_intro.tex}
\subfile{soc/soc.tex}
\subfile{core/core.tex}

\printbibliography

\end{document}