Your question is a good one, yet the answer is not a quick and simple one. There are different theories regarding young children and the developmental processes of early writing. I will only explain a little here, due to other posters may have different and useful info. to share.
Early writing is a completely normal stage of a young child's development. These pre-writings which we call scribbling, are the beginnings of communication and the precursor to reading. That is wonderful news that you have a child heavily involved in this stage of development. You may want to think about providing a multi purpose spot in your home for your child to either sit with you at a table and be allowed to draw on large pieces of paper. You could tape larger pieces of paper on the walls in that same area and allow for your child to use crayons, washable markers, chalk and washable finger paint. If you sit down with your child and engage in this process together by simply coloring a piece of paper and not really drawing anything specific, your child will stay with you in that designated space and you won't have to worry about him/ her drawing in other parts of the house. Getting into a routine will help. Also, I mentioned not drawing anything specific because you don't want to give your child a reason to feel as though their attempts at drawing or writing are wrong. Also, if you have a child size table near a wall, you can hang a mirror next to the table, which will also allow your child to observe their own hand position and watch the marks they make on paper from a different view point.
I know this was a lot. I hope this helps. I'm sure others have even more ideas to share. Good luck and enjoy this stage!