We tend to think of “the doctrine of Christ” as being some special separate piece of the gospel with its own special name. But that is not the case. It is exactly what it says it is. It is Christ’s doctrine. It is the same doctrine he was given by the Father as we read in 3 Nephi 11 and John 7.
John 7:16 Jesus answered them, and said, My doctrine is not mine, but his that sent me.
3 Nephi 11:32 And this is my doctrine, and it is the doctrine which the Father hath given unto me …
So we may as well just call it the doctrine of the Father. We would be just as accurate if we were to do so. The doctrine of Christ is the doctrine of his Father, as he obtained it from his Father. The doctrine of Christ isn’t a doctrine with a special name, it is simply exactly what it says it is. It is Christ’s doctrine.