Definition: Software product management is the process of managing software that is built and implemented as a product, taking into account life-cycle considerations and generally with a wide audience. It is the discipline and business process which governs a product from its inception to the market or customer delivery and service in order to maximize revenue. - Wikipedia
Study Note: the following resources try to give an 360 degrees knowledge to Software Product Management. In my personal opinion none of those, even together, fully accomplishes the goal. So, why have I included them into the stack? Because you should take them as introduction to the basics, not as a full knowledge of the matter.
I've been in this industry a long time and have never heard anyone talk about certifications for product managers (or engineers, program managers, sales, execs, or pretty much any role). I wouldn't waste your time worrying about it. The only thing that matters is being great at your job and having a reputation for being great. To get that, seek out great companies, mentors, and challenging projects. You may want to take some courses, read some books, or go to some conferences along the way, but only to the extent that they actually make you better, not as a credential in their own right. Don't worry about credentials that certify that you are good. Work on actually *being* good.
Why study for this syllabus? Although the field of Software Product Management is in everlasting evolution, by studying this syllabus you will get the basic concepts of Software Product Management.