[xsl] Processing tag text either side of nested tags

["Neil Crofts" <neil.crofts@xxxxxxxxx>]

I have some XML with text contained either side of a nested tag. I
would like to apply a named template to the text parts such that I
modify the text but also preserve the nested tags as-is. For example,
I have some XML of the form:

<outer> hello there <inner name="alpha">beta gamma</inner> goodbye then
</outer>

...and I need to transform it to the following format:

<outer> HELLO THERE <inner name="alpha">beta gamma</inner> GOODBYE THEN
</outer>

where in this case a named template converts the text to upper case,
although ideally the conversion function would be arbitrary.

I have made a number of attempts so far at doing this, but without
success. For example:

    <!-- Identity template -->
    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>

    <!-- Outer template -->
    <xsl:template match="outer">
        <xsl:copy>
            <xsl:copy-of select="@*"/>
            <xsl:call-template name="upper">
                <xsl:with-param name="text">
                    <xsl:apply-templates select="node()"/>
                </xsl:with-param>
            </xsl:call-template>
        </xsl:copy>
    </xsl:template>

    <!-- Convert text to upper case -->
    <xsl:template name="upper">
        <xsl:param name="text"/>
        <xsl:value-of select="translate($text,
'abcdefghijklmnopqrstuvwxyz', 'ABCDEFGHIJKLMNOPQRSTUVWXYZ')"/>
    </xsl:template>


The above results in:

<outer>HELLO THEREBETA GAMMAGOODBYE THEN</outer>

I understand why this is producing that, but I just can't figure out
how to apply the named template to only the text parts of the <outer>
tag, while copying the nested <inner> tag as-is.

Thanks in advance for any insight into how to resolve this problem.