YMMV, I believe most folks would call that "serialization," reserving "encoding" for turning a notionally written-down-ish representation into bytes; e.g. string -> utf8 bytes, or float -> IEEE-754 bytes.
Right, for some reason in Go (which Helm is written in), the standard library calls them encoders/decoders with marshal/unmarshal as the operations. Serialize is definitely the more common term generally.