tree 50993cec5b580162af0c1fadd4959abd84364d13
parent d9e094c305c8c0ddf722031b206c1175f0083730
author Tim 'mithro' Ansell <tansell@google.com> 1593623543 -0700
committer Tim 'mithro' Ansell <me@mith.ro> 1593832778 -0700

Add the standard cells as submodules.

They are being added as submodules from the
https://foss-eda-tools.googlesource.com/ repository due to their large
size. People are encouraged to only initialize and clone the submodules
needed for their designs.

 * [`sky130_fd_sc_hd`](https://github.com/google/skywater-pdk/tree/master/libraries/sky130_fd_sc_hd) -
   "High density" digital standard cells provided by the SkyWater
   foundry.

 * [`sky130_fd_sc_hdll`](https://github.com/google/skywater-pdk/tree/master/libraries/sky130_fd_sc_hdll) -
   "High density, low leakage" digital standard cells provided by the
   SkyWater foundry.

 * [`sky130_fd_sc_hs`](https://github.com/google/skywater-pdk/tree/master/libraries/sky130_fd_sc_hs) -
   "High speed" digital standard cells provided by the SkyWater foundry.

 * [`sky130_fd_sc_ms`](https://github.com/google/skywater-pdk/tree/master/libraries/sky130_fd_sc_ms) -
   "Medium speed" digital standard cells provided by the SkyWater
   foundry.

 * [`sky130_fd_sc_ls`](https://github.com/google/skywater-pdk/tree/master/libraries/sky130_fd_sc_ls) -
   "Low speed" digital standard cells provided by the SkyWater foundry.

Signed-off-by: Tim 'mithro' Ansell <tansell@google.com>