Does libx264 encoder support 12 bit pixel format such as yuv444p12le?

Libx264 show support for following input pixel formats:

yuv420p yuvj420p yuv422p yuvj422p yuv444p yuvj444p nv12 nv16 nv21 yuv420p10le yuv422p10le yuv444p10le nv20le gray gray10le

• For libx264 can support be added for 12 bit format like yuv444p12le?

• Any other open source encoder which supports 12 bit format?

x264 does not support 12-bit - it only does up to 10-bit; x265 does.