diff --git a/docs/proposed/psa-driver-interface.md b/docs/proposed/psa-driver-interface.md
index 5f0653a..044bf73 100644
--- a/docs/proposed/psa-driver-interface.md
+++ b/docs/proposed/psa-driver-interface.md
@@ -530,6 +530,16 @@
 
 When the driver requires entropy, the core can supply it with one or more successive calls to the `"add_entropy"` entry point. If the required entropy size is zero, the core does not need to call `"add_entropy"`.
 
+#### Combining entropy sources with a random generation driver
+
+This section provides guidance on combining one or more [entropy sources](#entropy-collection-entry-point) (each having a `"get_entropy"` entry point) with a random generation driver (with an `"add_entropy"` entry point).
+
+Note that `"get_entropy"` returns data with an estimated amount of entropy that is in general less than the buffer size. The core must apply a mixing algorithm to the output of `"get_entropy"` to obtain full-entropy data.
+
+For example, the core may use a simple mixing scheme based on a pseudorandom function family $(F_k)$ with an $E$-bit output where $E = 8 \cdot \mathtt{entropy_size}$ and $\mathtt{entropy_size}$ is the desired amount of entropy in bytes (typically the random driver's `"initial_entropy_size"` property for the initial seeding and the `"reseed_entropy_size"` property for subsequent reseeding). The core calls the `"get_entropy"` points of the available entropy drivers, outputting a string $s_i$ and an entropy estimate $e_i$ on the $i$th call. It does so until the total entropy estimate $e_1 + e_2 + \ldots + e_n$ is at least $E$. The core then calculates $F_k(0)$ where $k = s_1 || s_2 || \ldots || s_n$. This value is a string of $\mathtt{entropy_size}$, and since $(F_k)$ is a pseudorandom function family, $F_k(0)$ is uniformly distributed over strings of $\mathtt{entropy_size}$ bytes. Therefore $F_k(0)$ is a suitable value to pass to `"add_entropy"`.
+
+Note that the mechanism above is only given as an example. Implementations may choose a different mechanism, for example involving multiple pools or intermediate compression functions.
+
 #### Random generator drivers without entropy injection
 
 Random generator drivers should have the capability to inject additional entropy through the `"add_entropy"` entry point. This ensures that the random generator depends on all the entropy sources that are available on the platform. A driver where a call to `"add_entropy"` does not affect the state of the random generator is not compliant with this specification.