Within the context of the “legal system” of the Holy Roman Empire as established by the 1356 Golden Bull and the subsequent reform by the Imperial Diets, there were two methods of acquiring nobility that can be acquired (without usurping a currently-existing noble title of course), and the first is the granting of the title of an Imperial count or Reichsgraf [1]. This kind of nobility, from being an Imperial Knight to being a new Princely Count, is a reserved privilege of the Emperor only [1] [2].

However, another type of elevation is being a Graf or count. This kind of elevation is essentially a Princely lord (electors, dukes, Landgraves etc.) parceling out a piece of the land they currently own to another person in a feudal manner, for example how the King of Bohemia would have been able to parcel out direct land he controlled in Silesia and Moravia in his capacity as King of Bohemia, but not do so with the lands outside of the crown of Bohemia without having to use the powers of the Holy Roman Emperor [3], where this act of parceling out of a land (called Afterlehen) would create a noble under the prince that parceled out the land, creating a new noble under that particular Prince that is not directly subservient to the Emperor.

Sources:

[1] The Golden Bull of 1356; Translated and Scanned by The Avalon Project of Yale University (Link: https://avalon.law.yale.edu/medieval/golden.asp)

[2] Pine L.G., Titles: How did the King become His Majesty?

[3] Evans, Robert and Wilson, Peter The Holy Roman Empire, 1495-1806: A European Perspective