Antmicro recently released a sphinx domain for Verilog which enables you to write software style documentation for your Verilog / SystemVerilog code. When you combined it with a few other sphinx extension listed below, you get very nice looking docs.

• https://github.com/SymbiFlow/sphinx-verilog-domain
• https://github.com/SymbiFlow/sphinxcontrib-hdl-diagrams
• https://github.com/SymbiFlow/sphinx_symbiflow_theme
• https://github.com/SymbiFlow/symbolator
• https://github.com/SymbiFlow/sphinxcontrib-session
• sphinxcontrib-wavedrom

Some examples are;

• SymbiFlow documentation - https://SymbiFlow.rtfd.io
• SkyWater-pdk documentation - https://SkyWater-pdk.rtfd.io
• Fomu workshop - https://workshop.fomu.im