diff --git a/docs/global_substitutions.txt b/docs/global_substitutions.txt
index 242e62c..fdca9c3 100644
--- a/docs/global_substitutions.txt
+++ b/docs/global_substitutions.txt
@@ -38,6 +38,7 @@
 .. |SMCCC| replace:: :term:`SMCCC`
 .. |SoC| replace:: :term:`SoC`
 .. |SP| replace:: :term:`SP`
+.. |SPCI| replace:: :term:`SPCI`
 .. |SPD| replace:: :term:`SPD`
 .. |SPM| replace:: :term:`SPM`
 .. |SVE| replace:: :term:`SVE`
diff --git a/docs/glossary.rst b/docs/glossary.rst
index afe0acf..45caf46 100644
--- a/docs/glossary.rst
+++ b/docs/glossary.rst
@@ -129,6 +129,9 @@
    SP
       Secure Partition
 
+   SPCI
+      Secure Partition Client Interface
+
    SPD
       Secure Payload Dispatcher