The final text referenced by J. G. Frazer in the Golden Bough when discussing the “resurrection” of Dionysus was the Commentary on the Dream of Scipio by Macrobius. A kind correspondant has emailed me a page or two from Stahl’s English translation of this.
Part of what Frazer said is this (see a fuller discussion earlier):
In other [stories] it is simply said that shortly after his burial he rose from the dead and ascended up to heaven; …
 Macrobius, Commentarium in Somnium Scipionis i, 12, 12; …
So what does book 1, chapter 12, verse 12 say?
12. Members of the Orphic sect believe that material mind is represented by Bacchus himself, who, born of a single parent, is divided into separate parts. In their sacred rites they portray him as being torn to pieces at the hands of angry Titans and arising again from his buried limbs alive  and sound, their reason being that nous or Mind, by offering its undivided substance to be divided, and again, by returning from its divided state to the indivisible, both fulfills its worldly functions and does not forsake its secret nature.
20. Cf. Macrobius Saturnalia 1.xviii.15; Proclus (Diehl) 53C, 184E. See Lobeck, pp. 557, 711, 736; F. M. Cornford, From Religion to Philosophy (London, 1912), pp. 209-10; J. E. Harrison, Prolegomena to the Study of Greek Religion (Cambridge, England, 1922), pp. 489-90.
21. Following Eitrem’s reading vivus et integer, Nordisk Tidsskrift for Filologi, III ( r 915), 55. The MSS read unus et integer.
How I wish this translation was online!
Verse 12 is a little brief, so some explanation may be in order. The reference to “that material mind” is to the World Soul, and has been discussed in verse 6:
6. This is the condition that Plato called “at once indivisible and divisible” when he was speaking in the Timaeus about the construction of the World-Soul. Souls, whether of the world or of the individual, will be found to be now unacquainted with division if they are reflecting on the singleness of their divine state, and again susceptible to it when that singleness is being dispersed through the parts of the world or of man.
So lots of philosophical stuff there, but not relevant to Dionysus as such.
Returning to Macrobius Saturnalia, as the footnote suggests, we find this in book 1, chapter 18:
[ 1 3] Orpheus here has called the sun “Phanes” (φανερός), from its light and enlightening, for the sun sees all and is seen by all. The name Dionysus is derived, as the soothsayer himself says, from the fact that the sun wheels round in an orbit.  Cleanthes writes that the name Dionysus is derived from the Greek verb meaning “to complete” (διανύσαι), because the sun in its daily course from its rising to its setting, making the day and the night, completes the circuit of the heavens.  For the physicists Dionysus is “the mind of Zeus” (Διὸς νοῦς), since they hold that the sun is the mind of the universe; and by the universe they mean the heavens which they call Jupiter — and that is why Aratus, when about to speak of the heavens, says:
From Zeus be our beginnings. [Phaenomena I]
 The Romans call the sun Liber, because he is free (liber) to wander — as Naevius puts it:
Here where the wandering sun flings loose his fiery reins and drives nearer to the earth.
 The Orphic verses, too, by calling the sun “Eubouleus,” indicate that he is the patron of “good counsel”; for, if counsel is the offspring of the Inind and if, in the opinion of our authorities, the sun is the mind of the universe from which the first beginning of intelligence is diffused among mankind, then the sun is rightly believed to preside over good counsel.  In the line:
The sun, which men also call by name Dionysus
Orpheus manifestly declares that Liber is the sun, and the meaning here is certainly quite clear; but the following line from the same poet is more difficult:
One Zeus, one Hades, one Sun, one Dionysus.
 The warrant for this last line rests on an oracle of Apollo of Claros, wherein yet another name is given to the sun; which is called, within the space of the same sacred verses by several names, including that of Iao. For when Apollo of Claros was asked who ‘among the gods was to be regarded as the god called Iao, he replied:
 Those who have learned the mysteries should hide the unsearchable secrets, but, if the understanding is small and the mind weak, then ponder this: that lao is the supreme god of all gods; in winter, Hades; at spring’s beginning, Zeus; the Sun in summer; and in autumn, the splendid Iao.
 For the meaning of this oracle and for the explanation, of the deity and his name, which identifies Iao with Liber Pater and the sun, our authority is Cornelius Labeo in his book entitled On the Oracle of Apollo of Claros.
 Again, Orpheus, pointing out that Liber and the sun are one and the same god, writes as follows of the ornaments and vestments worn by Liber at the ceremonies performed in his honor:…
The syncretism which destroyed late paganism is certainly present in all that, as myths melt down into a puddle of meaningless names.
But note how the material from the Saturnalia does not, in fact, connect to the statement in the Commentary for which Stahl gives it as a reference!
We seem to be largely done with the resurrection of Dionysus. Nothing in this connects to the idea of a fertility god who rises in the spring.