yosys/docs/source/code_examples/intro/mycells.lib

library(demo) {
  cell(BUF) {
    area: 6;
    pin(A) { direction: input; }
    pin(Y) { direction: output;
              function: "A"; }
  }
  cell(NOT) {
    area: 3;
    pin(A) { direction: input; }
    pin(Y) { direction: output;
              function: "A'"; }
  }
  cell(NAND) {
    area: 4;
    pin(A) { direction: input; }
    pin(B) { direction: input; }
    pin(Y) { direction: output;
             function: "(A*B)'"; }
  }
  cell(NOR) {
    area: 4;
    pin(A) { direction: input; }
    pin(B) { direction: input; }
    pin(Y) { direction: output;
             function: "(A+B)'"; }
  }
  cell(DFF) {
    area: 18;
    ff(IQ, IQN) { clocked_on: C;
                  next_state: D; }
    pin(C) { direction: input;
                 clock: true; }
    pin(D) { direction: input; }
    pin(Q) { direction: output;
              function: "IQ"; }
  }
}